DEL.  190* 


UNIVERSITY  OF  CALIFORNIA 
AT  LOS  ANGELES 


GIFT  OF 

MRS. JOHN   G.SHEDD 


TESTS  OF  ELECTRIC  CAR  EQUIPMENT 


Companion   Volumes 

SHOP  TESTS  ON  ELECTRIC 
CAR  EQUIPMENT.  For  In- 
spectors and  Foremen. 

Price,  $1.00  Net 


MISCELLANEOUS  TESTS  OF 
ELECTRIC  CAR  EQUIPMENT 

Price,  $1.00  Net 


MISCELLANEOUS   TESTS 


OF 


ELECTRIC  CAR  EQUIPMENT 


BY 

EUGENE  C.   PARHAM,  M.  E. 

AND 

JOHN  C.  SHEDD,  Ph.D. 


McGRAW-HILL  BOOK  COMPANY 

239  WEST  39th  ST.,  NEW  YORK 

6  BOUVERIE  ST.,  LONDON,  E.  C. 

1910 


Copyright,  1910 

by  the 
McGRAW-HILL  BOOK  COMPANY 


PREFACE 


The  present  volume  is  the  second  of  two,  the 
first  being  entitled  "Shop  Tests  on  Electric  Car 
Equipment."  In  the  first  volume  many  of  the 
more  common  and  some  less  common,  but  useful, 
equipment  tests  were  so  described  as  to  be  readily 
available  to  men  of  limited  testing  facilities  and 
experience.  The  second  volume  continues  this 
effort  to  present  the  testing  subject  in  a  simple  and 
direct  manner  and  embodies  tests  and  explanations 
that  could  not  well  be  included  in  the  first  book.  It 
is  believed  that  the  two  books  cover  a  large  part  of 
the  equipment-testing  field  in  a  way  not  previously 
attempted,  both  in  the  manner  of  presentation  and 
in  that,  information  hitherto  scattered,  has  been 
brought  within  the  scope  of  two  comparatively 
small  books.  In  giving  numerous  rules,  examples, 
solutions,  directions,  notes  and  rehearsing  ques- 
tions, the  authors  have  tried  to  treat  the  subject  in 
a  practical  manner;  the  purpose  being  not  only  to 
reach  nonmathematical  readers,  but  to  give  mathe- 
matical readers  of  limited  experience  a  line  on  how 
such  tests  are  actually  made  with  the  facilities 
usually  available,  rather  than  how  they  might  or 
should  be  made  under  ideal  conditions.  If  these 
objects  have  been  accomplished  we  feel  that  the 
mission  of  the  book  has  been  attained. 

THE  AUTHORS. 
NEW  YORK, 
April  ist,  1910. 


206524 


TABLE    OF   CONTENTS 


PART  I— STATIONARY  TESTS 

CURRENT  COLLECTORS — 

Overhead  Trolley 1 

Conduit  System 4 

Third  Rail  System 6 

CAR  FUSES — 

Blowing  Tests 7 

Calculation  of  Fuse  Capacity 8 

Fuse  Test  Requirements 9 

CAR  CIRCUIT  BREAKERS — 

Periodic  Tests 10 

Adjustments 11 

Auxiliary  Apparatus 13 

CAR  CONTROLLERS — 

Mechanical  Tests 15 

Electrical  Tests 18 

Inspections 22 

CAR  STARTING  COILS — 

Ohmic  Resistance 25 

Changed  Conditions 29 

CAR  LIGHTNING  ARRESTERS — 

Connection  Tests 33 

CAR  WIRING  CABLES — 

Preliminary  Considerations 37 

Tagging  and  Insulation  Tests 39 

CAR  MOTORS — 

Brush  Holders  Requirements 42 

"         Irregularities 44 

"            "        Miscellaneous  Topics 51 

Motor  Insulation  Tests 55 

Circuit  Test 56 

Field  Coil  Polarity  Test 61 

Carbonized  Field  Coils 63 

Armature  Clearance 66 


vra  CONTENTS 

PART  II— MOTION  TESTS 

MOTOR  BALANCE  TESTS — 

Voltmeter  Method 70 

Lamp  Circuit  Method 74 

Ammeter  Method 76 

Milli-Voltmeter  Method 78 

Value  as  a  Field  Test 82 

MOTOR  HEATING  TESTS — 

Object  of  Heat  Test 83 

Test  Connections 84 

"     Instructions 86 

"     Readings 87 

EFFICIENCY  TESTS — 

Definitions 90 

Electrical  Efficiency  Test 91 

Commercial      "             "    92 

ENERGY  ABSORPTION  TESTS — 

Introductory 95 

Indicating  Wattmeter  Methods 96 

Voltmeter- Ammeter             "    97 

Record  Sheets 99 

Analysis  of  Test  Sheet 100 

MISCELLANEOUS  TESTS — 

Speed  Tests 112 

Acceleration  Tests 114 

Retardation  Tests 119 

Train  Resistance 122 

Horse  Power  of  Traction 125 

Total  Horse  Power  of  Operation 128 

HELP  TO  THE  INJURED — 

Reviving  Shocked  Persons 131 

Relieving  Burns 133 

Rehearsal  Questions 135 

Index 154 


INDEX  OF   RULES 


PAGE 

To  find  size  of  copper  fuse  wire 8 

"      "     "shocking" '  voltage 31 

"      "     area  of  brush  contact 50 

"      "     brush  pressure 51 

"      "     center  to  center  brush  count 53 

"      "     inside  brush  count 54 

"      "     per  cent,  difference  of  meter  readings 72 

"      "     number  of  lamps  for  given  voltage  on  balance 

test 74 

"      "     voltage  for  motor  in  balance  test 75 

"      "     speed  from  voltage  readings 87 

"      "     temperature  rise  from  rise  in  resistance 88 

"      "     degrees  Fahrenheit  from  degrees  Centigrade  .  89 
"      "           "        Centigrade  from  degrees  Fahrenheit  .  89 
"      "     per  cent,  efficiency  from  output  and  input ...  91 
"      "     electrical  efficiency  from  known  voltage  cur- 
rent and  resistance 91 

"      "     Watts  absorbed  in  brake  test 93 

"      "          "     input  of  motor  from  current  and  Volt- 
age readings 94 

"      "     watt  hours  from  indicating  wattmeter 97 

"      "     car  weight  in  tons  from  weight  in  pounds.  . .  .  101 

"      "     rated  horsepower  of  equipment 101 

"      "     time  in  hours  from  time  in  minutes 102 

"      "     average  voltage 103 

"      "          "        current  of  all  readings 104 

"        of  current  readings 104 

"      "           "        power,  in  watts,  of  all  readings 106 

"     "       "      of  power  readings ....  106 

"          "        car  speed 106 

"      "     watt  hours  absorbed 107 

IX 


x  INDEX  OF  RULES 

PAGE 

To  find  kilowatt  hours  from  watt  hours 107 

"      "     horsepower  hours  from  kilowatt  hours 107 

"      "     average  kilowatts  (or  kilowatt  hours  per  hour)  108 

"      "          "        kilowatt  hours  per  mile 108 

"      "          "  "         "         "   ton 109 

"      "          "        kilowatts  per  ton  (or  kilowatt  hours 

per  hour  per  ton) 109 

"      "     average  kilowatt  hours  per  ton-mile 110 

"      "     speed  in  miles  from  rail  count — 30-ft.  rails. .  .  112 

"      "         "       "        "       "      rail  count — 60-ft  rails. ...  112 

"      "        "       "        "       "      pole  count 113 

"      "        "       "        "         on  measured  track 113 

"      "     acceleration  in  miles  per  hour  per  second  ....  114 

"      "     retardation     "     "        "        "       "          "      120 

"      "     feet  per  second  per  second  from  miles  per  hour 

per  second 115,  120 

"      "     average  speed  during  acceleration 116 

"      "     maximum  "     due  to  116 

"      "     force  in  pounds  to  produce  given  acceleration 

in  miles  per  hour  per  second 117 

"      "     force  in  pounds  to  produce  given  acceleration 

in  feet  per  second  per  second 118 

"      "     horsepower  of  acceleration 118 

"      "     total  train  resistance 123 

"      "     grade  resistance 124 

'     average  horsepower  of  traction 125,  126 

'•'      "     horsepower  required  on  grade 127 

'      "     rise  in  feet  of  given  grade 127 

'      "     per  cent,  grade  from  known  rise 128 

'      "     total  horsepower  of  operation 128 


Miscellaneous  Tests  of  Electric 
Car  Equipment 

PART  I  STATIONARY  TESTS 

CURRENT  COLLECTORS 

OVERHEAD  TROLLEY 

1.  Rough   Pressure   Test.     The   trolley   wheel 
should  safely  engage  the  trolley  wire  at  all  heights. 
In  tunnels  and  culverts,  the  wire  may  be  low  and 
the  pressure  of  the  wheel,  excessive;  at  steam  road 
crossings,  the  wire  may  be  high  and  the  pressure 
so  weak  that  the  wheel  jumps — a  dangerous  con- 
dition.   The  rough  pressure  test  is  to  try  the  pres- 
sure when  the  pole   is   almost  vertical:  the  test  is 
made  as  follows: — 

2.  Directions.     To    apply    the   rough   test   for 
trolley  pole  contact  pressure,  Pay  out  the  rope  and 
let  the  pole  go  to  a  vertical  position;   if  it  does  so 
promptly,  the  pressure  is  sufficient  for  all  condi- 
tions. Tf  not,  Increase  the  pressure  with  the  adjust- 
ing nut  and  repeat  the  test. 

3.  Scale  Pressure  Test.     This  test  is  made  with 
a  spring  scale  on  which  can  be  read  the  pounds  pull 
required  to  just  lower  the  wheel  from  a  stretch  of 
wire  of  standard  height. 

4.  Directions.     To  measure  the  pressure  of  the 
trolley  wheel  against  the  wire  with  a  spring  scale, 

1 


2  MISCELLANEOUS  TESTS  OF 

Apply  the  scale  to  the  wheel  at  right  angles  to  the 
wire  and  read  the  scale  when  the  wheel  is  just  held 
from  the  wire. 

Fig.  1  shows  how  to  apply  the  scale.  The  upward 
force  with  which  the  wheel  presses  the  wire  depends 
on  the  strength  of  the  spring,  the  length  of  the  pole 
and  the  angle  it  makes  with  the  top  of  the  car.  To 
read  the  pressure  directly,  the  scale  must  stand  at 
right  angles  to  the  wire  or  along  line  b  in  Fig.  1. 
The  vertical  pull  required  to  lower  the  wheel  from 


the  wire  exceeds  the  pull  along  line  d,  at  right 
angles  to  the  pole,  but  it  gives  the  actual  pressure  of 
the  wheel  against  the  wire.  The  reading  when  the 
scale  is  applied  along  line  d  is  smaller  than  along 
any  other  line,  as  b  or  c.  This  is  shown  by  Table 
I.  The  stretch  of  test  wire  must  be  at  standard 
height  and  the  wheel  must  rest  under  a  section  free 
from  sag,  otherwise,  when  the  pull  is  applied,  the 
wire  will  follow  the  wheel  down  and  break  contact 
where  the  pressure  is  greater  than  at  standard 
height.  To  get  uniform  results,  all  tests  must  be 
made  under  the  same  stretch  of  wire.  Formerly, 
the  height  of  wire  and  length  of  poles  were  such  as 


ELECTRIC  CAR  EQUIPMENT 


to  give  a  pole-roof  angle,  /  (Fig.  1)  of  about  45°; 
but  increased  height  of  cars  and  length  of  poles 
without  corresponding  increase  in  height  of  wire 
have  reduced  this  angle. 

5.  Pressure  Measurements.  Table  I  gives 
readings  on  a  12-foot  pole  with  roof  angles  of 
approximately  45°  and  30°.  Where  the  pole-roof 

TABLE  I 


ROOF  ANGLE  45° 

ROOF  ANGLE  30° 

Pull  in  Lbs. 
Rt.  Angle  to  Pole 

Pull  in  Lbs. 
Rt.  Angle  to  Wire 

Pull  in  LI:  s. 
Rt.  Angle  to  Pole 

Pull  in  Lbs. 
Rt.  Angle  to  Wire 

29.3 

40 

34.0 

40 

25.0 

35 

30.0 

35 

21.0 

30 

26.0 

30 

18.0 

25 

21.5 

25 

14.0 

20 

17.0 

20 

11.0 

15 

13.0 

15 

angle  does  not  approach  either  of  these  values, 
the  vertical  pull  for  adjusting  the  trolley  pole 
pressures  of  cars  can  be  obtained  by  following  the 
directions  given  below — 

6.  Directions.     To  adjust  trolley  pressures  to 
equal  standard  values,  Run  a  standard  car  under  a 
standard  stretch  of  wire  and  adjust  the  vertical 
pull   to   the   desired   value — 30   Ib.    for   example. 
Thereafter,  all  standard  cars  adjusted  under  the 
test  wire  to  give  a  vertical  pull  of  30  Ib.  will  have 
the  desired  pressure. 

7.  Remarks.     Trolley  pole  pressures  on  differ- 
ent roads  are  as  different  as  are  the  opinions  as 
to  what  their  values  should  be;  on  the  same  road, 


4  MISCELLANEOUS  TESTS  OF 

pressures  are  different  owing  to  varying  car  heights, 
pole  lengths  and  neglect  of  adjustment.  Excessive 
pressure  unduly  wears  both  wheel  and  wire,  makes 
the  pole  hard  to  replace  under  the  wire  and  invites 
damage  to  pole  and  line  when  the  wheel  jumps  the 
wire.  Deficient  pressure  impairs  the  centering 
action  of  the  device  and  makes  it  easier  for  a  kink 
in  the  wire,  a  rough  trolley  wheel  groove  or  rough 
track,  to  throw  the  wheel  from  the  wire.  The  best 
pressure  is  determined  by  experiment;  it  increases 
with  the  car  speed  because  the  higher  the  speed 
the  greater  the  blows  due  to  irregularities:  the 
pressure  must  be  sufficient  to  restore  the  wheel 
before  the  impact  of  a  blow  can  force  it  down  a 
distance  exceeding  the  depth  of  the  wheel  groove. 
In  city  service  the  pressure  used  varies  from  20  to 
30  Ib. ;  in  interurban  high  speed  service,  from  30 
to  50  Ib. 

CONDUIT  SYSTEM 

8.  The    current    collector   used    on    a    conduit 
system  is  called  a  plow.    The  tests  to  which  plows 
as   a   whole   are    subjected    are   the    contact-shoe 
pressure-test  and  the  insulation-test. 

9.  Pressure  Test.     The  test  used  in  a  car  house 
consists  in  the  slapping  of  the  springs  together  by 
hand  to  see  that  they  are  neither  weak  nor  broken 
and  that  the  action  is  free.    The  distance  apart  of 
the  slot  conductors  is  6  inches ;  the  distance  between 
contact  shoe  surfaces  on  a  standard  plow,  dimension 
a,  Fig.  2,  is  8Xm-    In  service,  then,  each  spring  is 
compressed    \%  in.     To   do   this,   a  pressure  of 


ELECTRIC  CAR  EQUIPMENT  5 

approximately  25  Ib.  is  required.  As  the  shoes 
have  a  wearing  surface  of  about  10  sq.  in.,  the 
pressure  per  sq.  in.  is  2.5  Ib.  Knowing  the  amount 


FIG.  2  FIG.  3 

of  compression,  the  desired  pressure  per  sq.  in. 
and  the  area  of  the  contact  shoe  surface,  a  shop 
pressure  test  can  be  made  as  follows: — 

10.  Directions.     Given  the  shoe  contact  surface 
area  in  sq.  in.  and  the  desired  pressure  per  sq.  in., 
Multiply  them  together  to  get  the  total  pressure  in 
pounds;    this  pressure  in  the  form  of  a  weight  is 
then  applied  to  the  spring  and  should  produce  a 
compression  of  1^  in.    If  the  compression  is  greater, 
the  spring  is  weak;   if  less,  the  spring  is  too  strong. 

11.  Insulation  Test.     Insulation  is  best  tested 
with  a  voltmeter,  but  a  lamp  test  circuit  is  gener- 
ally applied  as  follows: — 

12.  Directions.     To  test  plow  insulation  with 
test    lamps,    connect   the  lamps  as  indicated   in 
Fig.  3.     The  test  points  are  first  touched  together 
to  see  that  the  test  circuit  is  all  right.     Next,  test 
the  insulation  between  the  shoes  and  between  each 
shoe   and  the  iron   sheathing  of  the  plow  body. 
Finally,   touch   each   shoe  and  its  corresponding 


6  MISCELLANEOUS  TESTS  OF 

body  terminal,  to  see  that  the  circuit  between  them 
is  intact,  as  indicated  by  the  lighting  of  the  test 
lamps. 

13.  Remarks.     When   using  a  metallic  return 
system  as  a  source  of  voltage  with  which  to  test 
the  insulation  of  any  device,  it  is  well  to  hang  the 
device  up  or  to  lay  it  upon  wood,  to  minimize  the 
danger  of  a  shock  or  burn  should  one  side  of  the 
system    be    grounded,    as    is    generally    the    case. 
(See  Fig.  37,  "Shop  Tests  on  Electric  Car  Equip- 
ment").     It  is  on  this  account  that  half   of    the 
test  lamps  are  connected  in  each  of  the  test  lines — 
Fig.  3. 

THIRD  RAIL  SYSTEM 

14.  The  pressure  of  the  contact  shoe  used  on  a 
third  rail  system  is  due  either  to  the  weight  of  the 
shoe,   25   or   30   lb.,   or  to  an   equivalent   spring, 
the  latter  being  used  where  the  rail  is  housed. 
The  main  feature  of  inspection  here  is  the  shunt, 
provided  to  keep  the  shoe   pins  and    links   from 
carrying  sufficient  current  to  blister  and  thereby 
roughen  them. 


CAR  FUSES 
BLOWING  TESTS 

15.  Instantaneous  Test.  This  test  is  made  to 
determine  the  approximate  value  of  the  current 
required  to  blow  a  given  fuse  instantaneously. 


Var.  Resistance. 
FlG.  4 

The  connections  are  shown  in  Fig.  4,  where  x  is 
the  fuse  and  K,  a  quick-break  switch,  or  breaker. 
The  test  is  made  as  follows : — 

16.  Directions.     To    determine    the    value    of 
the  current  required  to  blow  a  given  fuse  instan- 
taneously, Repeatedly  insert  fuses,  close  K,  adjust 
R  and  open  k,  switch  k  being  closed  as  soon  as  the 
fuse  blows,  so  that  the  current  that  blew  the  fuse  can 
be  read  on  the  ammeter,  A. 

17.  Time  Element  Test.     The  time  element  of 
a  fuse  is  the  time  elapsing  between  the  closing  of 
the  circuit  (in  this  case)  and  the  blowing  of  the 
fuse.    The  test  is  made  as  follows : — 

18.  Directions.     To  make  a  time  element  test 
with  the  connections  of  Fig.  4,  Adjust  R  to  give  a 

7 


8  MISCELLANEOUS  TESTS  OF 

current  certain  to  blow  the  fuse  promptly;  then 
open  k  and  close  K;  now  repeatedly  insert  fuses, 
adjust  R,  open  k  and  close  K,  noting  the  time  with 
a  stop-watch,  elapsing  between  the  closing  of  K 
and  the  blowing  of  the  fuse,  until  the  time  elapsed 
is  the  time  element  desired. 

19.  Note.     This  test  is  useful  where  it  is  desired 
to  so  fuse  a  car  that  the  fuse  will  blow  a  certain 
number   of   seconds   after   the   current   for   which 
the  breaker  is  set  may  have  maintained,  owing  to 
the  breaker  being  out  of  order. 

20.  Operating  Test.     This  test,  of  more  value 
than  either  of  the  preceding,   consists  in  fusing 
cars  under  actual  operating  conditions  and  noting 
their  behavior  under  proper  handling.     Too  large 
a  fuse  affords  little  protection  to  equipment;    too 
small  a  fuse  causes  prohibitive  delay  in  replace- 
ments.     Cars   of   different    capacity    and    weight 
should  be  protected  by  different  capacities  of  fuse. 

CALCULATION  OF  FUSE  CAPACITY 

21.  The  approximate  size  of  copper  wire  to  be 
used  as  a  fuse  to  protect  an  equipment  of  given 
h.p.,  operating  under  average  conditions,  can  be 
found  by  applying  the  following  rule : — 

22.  Rule.     To  find  the  size  of  copper  fuse  wire 
for  an  equipment  of  given  h.p., Multiply  the  motive 
power  of  the  equipment  by  70  and  find  the  number 
nearest  to  this  product  in  the  circular  mils  column 
of  a  B  &  S  wire  table ;  opposite,  will  be  the  size  of 
wire  required. 


ELECTRIC  CAR  EQUIPMENT  9 

23.  Example.     What  size  of  copper  wire  should 
be  used  for  a  fuse  on  a  car  equipped  with  4  fifty 
h.p.  motors? 

24.  Solution.     4X50  =  200  h  p.  and  200X70  = 
14,000.    The  number  nearest  to  this  in  a  B  &  S  wire 
table  is  12,996,  which  corresponds  to  a  No.  9  wire. 

25.  Note.     This  rule  does  not  apply  to  cases 
where  two  or  more  wires  are  twisted  together,  as  the 
capacity  of  such  a  fuse  depends  upon  how  tightly 
the  wires  are  twisted. 

FUSE  TEST  REQUIREMENTS 

26.  Copper  wire  is  commonly  used  for  fuses, 
because  it  is  cheap,  uniform    in    diameter,   easy 
to  install,  and  is  in  no  way  special.     Except  under 
well  defined  conditions,  data  on  fuse  blowing  may 
be  misleading,  because  the  blowing  value  depends 
upon  the  length  of  fuse,  purity  of  the  copper,  size 
of    fuse    terminal    blocks,    method    of    fastening, 
position  and  location  of  the  fuse  box  and  upon 
whether  there  are  forces  provided  to  pull  the  fuse 
apart  when  it  softens.     To  find  the  size  of  the 
wire  to  be  used  in  a  given  fuse  box,  all  tests  should 
be  made  on  that  type  of  box  and  under  the  same 
conditions. 


CAR  CIRCUIT-BREAKERS 

ADVANTAGES  OF  PERIODIC  TESTS 

27.  Certainty  of  the  good  condition  of  car 
breakers  has  the  following  advantages : — In  damage 
suits  based  on  real  or  imaginary  injuries  caused 
primarily  by  fright  due  to  blowing  of  a  fuse,  con- 
troller short-circuit  or  other  demonstration,  ability 
to  prove  regular  breaker  inspection  has  weight  with 
judge  and  jury.  Adjusted  breakers  compel  the 
motorman  to  handle  the  controller  carefully;  this 
saves  energy,  because  a  too  rapid  advancement 
of  the  controller  increases  the  current  at  so  fast  a 
rate  that,  except  where  stops  are  few,  the  speed 
never  reaches  a  value  corresponding  to  existing 
load  conditions.  With  good  breaker  adjust- 
ment, the  maximum  current  per  car  is  fixed, 
thereby  decreasing  the  peak  of  the  current  demand 
of  that  car  on  the  station.  With  good  breaker 
adjustment  a  car  will  be  "run  in"  promptly  for 
a  slight  irregularity  that  would  become  serious 
were  it  permitted  to  persist.  Fixing  the  maximum 
current  per  car  minimizes  the  chances  of  excessive 
current  causing  a  burn-out  likely  to  frighten 
platform  passengers  to  the  point  of  jumping  from 
a  moving  car.  Good  adjustment  decreases  the 
liability  of  fire.  It  gradually  educates  motormen 
to  careful  handling  of  controllers,  so  that  the  current 
value  of  the  adjustment  can  be  decreased  toward 
10 


ELECTRIC  CAR  EQUIPMENT 


11 


a  point  where  the  maximum  possible  current  does 
not  greatly  exceed  the  overload  current  for  which 
the  motors  are  rated. 

CIRCUIT-BREAKER  ADJUSTMENTS 

28.  Ammeter  Method.  This  test  is  made  with 
the  connections  of  Fig.  5,  where  K  is  a  switch  or 
breaker;  A,  an  ammeter  of  range  exceeding  the 
test  current;  F,  a  fuse  or  breaker;  R,  a  water 
resistance;  r,  an  auxiliary  resistance  which,  in 


Fuse 


t' 


FIG.  5 


conjunction  with  switch  k,  affords  a  quick  means 
of  approximating  full  test  current.  By  means  of 
test  lines  t  and  t',  the  test  circuit  is  connected  in 
series  with  the  car  breaker  to  be  tested.  Assuming 
an  adjustment  of  250  amperes,  with  a  line  voltage 
of  500  volts,  if  r  is  2.5  ohms,  there  will  be  a  current 
of  200  amperes  on  closing  k  and  K,  leaving  but  50 
amperes  to  be  carried  by  the  water  rheostat. 
29.  Directions.  To  adjust  car  breakers  with 
the  connections  of  Fig.  5,  Adjust  r  to  give  90  per 
cent,  of  the  current.  With  all  switches  open,  the 
water  box  plates  pulled  apart,  the  test  lines  on  the 


MISCELLANEOUS  TESTS  OF 


closed  breaker  to  be  tested  and  the  ammeter  con- 
nected to  deflect  in  the  proper  direction,  close  k, 
then  K  and  adjust  R  until  the  ammeter  indicates 
250  amperes  or  the  car  breaker  opens.  Repeat 
these  operations  until  the  car  breaker  is  adjusted 
to  act  within  5  per  cent,  of  250  amperes. 

30.  Limit  Breaker  Method.  The  preceding  test 
is  reliable,  but  is  slow  and  requires  an  ammeter  which 
is  not  always  available.  Fig.  6  shows  the  connections 
of  the  limit  breaker  method,  which  requires  a 
meter  only  initially  for  adjusting  breakers  A  and  B. 
All  other  letters  mean  the  same  as  in  Fig.  5.  Assum- 


T 


FIG.  6 


ing  that  the  car  breakers  are  to  be  adjusted  for 
300  amperes,  limit  breaker  A  would  be  set  for  275 
and  B  for  325  amperes,  the  test  being  made  as 
follows : — 

31.  Directions.  To  adjust  car  breakers  with 
the  test  connections  of  Fig.  6,  Connect  the  car 
breaker  in  series  with  the  test  circuit;  close  all 
breakers,  then  switches  k  and  K;  handle  r  and  R  as 
in  the  preceding  test;  repeat  the  blowing  of  the 
car  breaker  and  its  readjustment,  until  it  operates 


ELECTRIC  CAR  EQUIPMENT 


13 


between  breakers  A  and  B.     This  done,  the  car 
breaker  is  adjusted. 

32.  Note.      Switch    x,     Fig.     6,    is    a    short- 
circuiting  path,  from  the  negative  side  of  the  blow- 
out coil  to  the  negative  terminal  of  the  breaker, 
to  bridge  the  breaker  contacts,   so  that  when  it 
acts  it  will  not  open  the  circuit,  but  will  serve 
simply  as  a  signal. 

AUXILIARY  APPARATUS 

33.  The  Water  Rheostat.     Any  form  of  water 
rheostat  having  a  cross-section  of  6  sq.  ft.  and  an 
inside  length  of  5  ft.  will  answer  for  breaker  and 
miscellaneous  tests  requiring  a  large  current  with- 
out foaming.     For  making  the  water  conducting, 
table  salt  is  added,  a  handful  at  a  time  as  needed. 
When  the  resistance  of  the  box  becomes  too  low, 
water  is  drawn  off  and  cold  water  admitted.     In 
out-of-door  testing  where  steam  and  foam  are  not 
objectionable,  a  barrel  can  be  used. 

34.  Attaching  Test  Lines   (First  Method).      In 
breaker  testing  the  test  lines  must  be  connected 


Car 

•^Breaker 


FIG.  7 

to  the  car  breaker.     This  is  best  done  by  baring 
the  breaker  wires  for  a  short  distance  and  placing 


14  MISCELLANEOUS  TESTS  OF 

lengths  of  garden  hose  over  the  bare  places  so  that 
they  Tvill  be  easy  to  shove  along  when  applying 
the  test  lines.  In  Fig.  7,  all  letters  mean  the  same 
as  in  Figs.  5  and  6,  test  line  t  being  connected  to 
the  +  side  of  the  breaker  to  be  tested  and  t',  to 
the  —  side  of  the  supply  circuit.  This  method  is 
the  most  general,  being  applicable  to  all  systems 
and  with  minimum  chances  of  contact  troubles. 

35.  Attaching  Test  Lines  (Second  Method).     To 
test  breakers  on  a  ground  return  car,  test  line  t  may 
end  in  a  hook  to  engage  the  trolley  wheel;    the 
pole  is  lowered,  the  motors  cut  out  in  a  controller, 
to  prevent  starting;    one  controller  placed  on  the 
last  parallel  notch,  to  save  the  car  starting  coil  and 
wires,  and  the  brake  set  as  a  factor  of  safety.    All 
current  must  pass  through  the  test  circuit  including 
the  water  rheostat,  the  adjustment  being  the  same 
as  already  described. 

36.  Note.     Other    methods    of    attaching    the 
test  lines  may  be  suggested  by  local  conditions. 
On  a  slot  system,  the  two  breakers  can  be  tested  one 
at  a  time  by  placing  one  test  line  on  a  plow  shoe 
and    the    other   on   the    corresponding    controller 
trolley  cdhnecting-post. 


CAR  CONTROLLERS 

MECHANICAL  TESTS 

37.  Cylinder    Interlocks.      Modern    controllers 
require  that  the  main  cylinder  at  the  "off"  position 
be  immovable  when  the  reverse  cylinder  is  at  the 
"off"  position;    and  that  the  reverse  cylinder  be 
immovable  when  the  main  cylinder  is  on  a  current 
notch.    The  first  condition  compels  the  motorman 
to  lock  his  controller  when  leaving  it  and  prevents 
reverses  on  opposite  ends  from  being  set  to  oppose 
each  other,  unless  this  has  been  maliciously  or 
accidentally    done    with    a    wrench.    The    second 
condition  prevents  reversing  without  first  throwing 
off  the  power,  reverse  switches  not  being  constructed 
to  break  an  arc  and  it  being  unwise  to  reverse 
with  power  on,  owing  to  increased  liability  of  blow- 
ing the  fuse  or  circuit-breaker. 

38.  Directions.     To  test  the  proper  condition 
of  the  controller  interlocks;  see   that  the  reverse 
handle  is  immovable  when  the  controller  handle  is 
on  a  current  notch  and  that  the  controller  handle  is 
immovable  when  the  reverse  handle  is  in  the  "off' 
position. 

39.  Cutout-Switch  Interference.     When  either 
cutout-switch  is  operated,  it  moves  an  interference 
that  prevents  advancement  of  the  main  cylinder 
beyond   the   last   series   notch.      Defective   inter- 
ference may  result  in  irregular  circuits,  in  burning 
of  tips  and  fingers  and  in  jerking  the  car. 

15 


16 


MISCELLANEOUS  TESTS  OF 


40.  Directions.      To  insure  good   condition   of 
the  interference,  operate  the  cutout-switches  one 
at  a  time,  in  each  case  seeing  that  the  cylinder 
cannot  be  moved  past  "series." 

41.  Alinement  Requirements.     Alinement  tests 
are  made  in  order  to  see  that  the  main  fingers  line 
up  vertically  with  each  other;    that  the  reverse 
fingers  line  up  vertically  with  each  other;    that 
all  fingers  line  horizontally  with  the  corresponding 
tips  and  that  all  contacts  intended  to  be  made 
simultaneously  are  so  made. 

42.  Vertical   Alinement.      With   a   well    alined 
cylinder    as    a    gage,    vertical    alinement    of    the 
fingers  can  be  judged  by  the  eye,  by  repeatedly 
moving  the  cylinder  "on"  and  "off"  and  noting 
how  the  fingers  touch.      Alinement  can  also  be 
judged  with  a  straight  edge,  as  in  Fig.  8,  care  being 


FIG.  8 


FIG.  9 


taken  to  hold  the  straight  edge  vertically.  By 
mounting  the  straight  edge  on  a  shaft  to  be  installed 
like  a  cylinder,  as  in  Fig.  9,  a  true  test  can  be  made. 
On  request,  the  factory  will  provide  jigs  for  aline- 
ment testing.  In  the  case  of  the  reverse  fingers, 
alinement  by  eye  will  usually  do. 


ELECTRIC  CAR  EQUIPMENT  17 

43.  Horizontal  Alinement.  The  test  for  hori- 
zontal alinement  is  made  by  the  eye  and  consists 
in  seeing  that  no  one  of  the  fingers  is  above  or  below 
its  corresponding  tip,  Fig.  10,  or  across  the  tip,  as 
in  Fig.  11.  The  first  condition  may  be  due  to  wear 
in  the  lower  cylinder  bearing,  to  error  in  the  cyl- 
inder or  finger  board  or  to  the  board  being  set  too 
high  or  too  low.  The  second  condition  is,  on  the 
main  cylinder,  generally  local  to  a  finger  or  two 


FIG,  10  FIG,  11 

and  can  be  corrected  by  straightening  the  finger. 
On  the  reverse,  horizontal  alinement  defects  are 
common,  owing,  probably,  to  the  fact  that  as  this 
cylinder  does  not  have  to  break  an  active  circuit, 
less  care  is  taken  to  keep  its  dimensions  standard. 
The  reverse  fingers  and  contacts  should  register 
truly,  because  they  carry  as  much  current  as  many 
of  the  main  fingers,  are  closer  together  and  very 
liable  to  contact  troubles. 

44.  Notch  Spacing.  This  term  refers  to  the  arc 
through  which  the  tips  move  when  the  cylinder  is 
advanced  a  notch.  It  can  be  judged  by  the  eye  if 
the  vertical  alinement  of  the  fingers  is  correct.  The 
vertical  alinement  may  be  good,  but,  owing  to  the 
fingers  being  too  long  or  too  short  or  to  the  board 


18  MISCELLANEOUS  TESTS  OF 

being  too  close  to  the  cylinder  or  too  far  from  it,  or 
to  the  index  wheel  being  in  error,  the  fingers  may 
fail  to  make  flush  contact  on  one,  several  or  all 
notches.  In  Fig.  12  the  fingers  on  the  first  position 
do  not  extend  far  enough,  while  in  Fig.  13,  they 

TfrH  <Dfc>;| 
finger  -/ 

FIG.  13 

extend  too  far,  with  the  result,  in  the  latter  case, 
that  when  the  cylinder  is  moved  from  "off  "position, 
it  will  jump  a  little  over  the  first  notch,  make  the 
combinations  of  the  second  notch,  disconcert  pas- 
sengers by  jerking  the  car,  and  burn  the  contacts. 
If  the  fingers  register  on  some  notches  but  not  on 
others,  it  points  to  error  in  the  cylinder.  Any 
failure  to  register  in  every  position  must  be  inves- 
tigated and  the  trouble  removed. 

ELECTRICAL  TESTS 

46.  Open-circuit.  The  open-circuit  test  is  made 
to  see  that  all  fingers  and  posts  that  should  be 
connected  are  connected;  it  is  made  with  a  lamp 
or  bell  circuit  and  requires  either  familiarity  with 
the  controller  internal  connections  or  ability  to  use 
a  sketch  like  that  of  Fig.  14,  a  sketch  of  the  internal 
connections  of  the  K  10-K  11  controllers.  This 
sketch  shows  the  T  post  connected  to  the  bottom 
of  the  blow-out  coil,  M,  the  top  of  which  connects 
to  finger  T;  also  finger  Rt  connects  to  post  Rt; 
fingers  R5  and  19,  to  the  top  left-hand  post  of  No. 
1  cutout-switch,  also  to  connecting-board  post 


ELECTRIC  CAR  EQUIPMENT 


19 


R5;  finger  15,  to  the  top  left-hand  post  of  No.  2 
cutout-switch,  also,  through  the  switch,  to  reverse 
finger  15  and  so  on,  each  post  or  finger  being  con- 


FIG,  14 

nected  to  another  post  or  finger.   The  open-circuit 
test  can  be  made  as  directed  below: — 

46.  Directions.     To     test     controller    internal 
connections  for  open-circuit,  Apply  one  test  point 
to  any  post  or  finger  and  the  other  to  the  post  or 
finger  to  which  the  first  is  supposed  to  be  connected, 
both  cylinders  being  at  "off  "  position:  if  the  lamps 
fail  to  glow,  the  cause  must  be  located  and  removed. 

47.  Complete    Circuit.  .    The    complete    circuit 


20  MISCELLANEOUS  TESTS  OF 

test  includes  both  cylinders  and,  on  the  controller 
bench,  is  made  as  follows: — 

48.  Directions.     To  test  a  controller  for  com- 
plete-circuit through  both  cylinders,  Short  circuit 
the  posts  ordinarily  connected  by  the  car  devices; 
put  the  reverse  on  an  operating  position  and  the 
main  cylinder  on  notch   1;    place  one  test  point 
on  connecting  post  T  and  touch  the  other  to  the 
successive   points   of  the   current   path   indicated 
below ;  the  lamps  will  glow  until  the  free  test  point 
passes  an  open-circuit. 

49.  Xote.     On  the  K  10-K  11  controllers,  with 
jumpers    between    Aj-AA^    Fj-Ej,    A2-AA2,    F2-G 
and  R^Rs,  the  test  current  path  is  T-M-T-cylinder- 
Ri-Rs-lQ-lQ-lO-reverse  cylinder  -  Ar  At  -  AAt  -  AA  x  - 
AAt  -  reverse    cylinder  -  Ft  -  F!  -E  rE  rE  rE  r  cylin- 
der- 15-15-15-  15-reverse   cylinder- A  2  -  A  2  -A  A  2- A  A  2- 
reverse    cylinder-F2-F2-F2-G.        Suppose    the    test 
lamps  to  glow  in  each  case  until  contact  with  the 
reverse  tip  under  fingers   Fx  and  AA1:    the  open- 
circuit  would  lie  between  finger  AAt  and  the  reverse 
tip  and  pressing  the  finger  down,  thereby  closing 
the  circuit,  would  light  the  lamps.     The  test  can 
be  applied  on  all  notches,  in  both  reverse  positions 
and  with  the  cutout-switches  cut  out  one  at  a  time. 

50.  Short-circuit.      With   a   knowledge  of  the 
internal  connections  or  the  aid  of  a  diagram,  the 
short-circuit  test  is  as  follows: — 

51.  Directions.     To     test     controller     internal 
connections  for  short-circuit,  Hold  one  test  point 
on  any  finger  or  post;    then  touch  the  other  to  all 


ELECTRIC  CAR  EQUIPMENT  21 

other  fingers  and  posts;  in  no  case  should  the  lamps 
glow  between  parts  not  normally  connected. 

52.  Ground.     A  ground  is  a  special  case  of  short- 
circuit;  on  a  bench  the  test  for  ground  is  made  as 
follows  :  — 

53.  Directions.     To     test     controller     internal 
connections  for  ground,  Hold  one  test  point  on  the 
frame  and  touch  the  other  successively  to  all  posts 
and  fingers;    the  lamps  should  fail  to  glow  except 
when  contact  is  made  with  a  part  marked  G. 

54.  Note.     Where  controller  benches  are  metal 
covered    and    in    contact    with    grounded    pipes, 
judgment  must  be  used  when  the  source  of  voltage 
is  a  ground  return  or  a  grounded  metallic  return 
circuit,  for  should  the  test  point  in  contact  with  the 
controller  frame  happen  to  be  "trolley"  the  lamps 
will  glow  although  the  controller  may  have  no  fault. 
Thus  in  Fig.  15,  T  is  the  positive  side  of  a  metallic 


Lining,  I 


FIG.  15 

return  circuit  of  which  the  negative  side  is  grounded 
at  G.  The  metal  bench  cover  is  1;  p,  a  gas  pipe;  n 
the  controller  frame;  /,  a  finger  and  i,  the  finger 
board.  If  in  testing  /  for  ground,  t  be  touched  to 
the  finger  and  /'  to  the  frame,  the  test  lamp  indi- 


22  MISCELLANEOUS  TESTS  OF 

cation  would  be  correct ;  but  should  t'  be  touched  to 
/  and  t  to  n,  the  lamps  will  glow  the  instant  t  touches 
n  whether  /'  has  yet  touched  anything  or  not 

INSPECTIONS 

55.     Main  Features.    The  main  features  of  con- 
troller inspection  are : — 

1.  Back  and  door  linings  to  be  intact. 

2.  All  iron  painted  and  clean. 

3.  Charred   parts  scraped   and   shellacked  or 

renewed. 

4.  Partitions  scraped  and  filled  or  renewed. 

5.  Fiber  separator  between  cylinders  o.  k. 

6.  Fingers  trimmed,  alined,  renewed  and  pres- 

sure adjusted. 

7.  Interlocks  and  interference  perfect. 

8.  Action  of  notching  mechanism  prompt  and 

decisive. 

9.  Soldered  joints  perfect. 

10.  Wire  insulation  intact. 

11.  Cylinder  castings  tight  on  shaft. 

12.  Blow-out  coil  in  good  shape. 

13.  Cutout-switches  o.  k.  and  workable  by  hand. 

14.  Door  a  good  fit  and  the  wing  nuts  turnable. 

15.  Blow-out  magnet  wrench  screwed  home. 

16.  Arc  deflectors  free  from  interference  with 

fingers. 

17.  Controller  top  tight. 

18.  Cylinder  bearings  o.  k. 

19.  Water  guards  in  place. 

20.  Cylinder  tips  alined  and  tight. 

21.  Handles  to  fit. 


ELECTRIC  CAR  EQUIPMENT  23 

56.  Precautions.     On  a  car,  the  controller  and 
brake  staff  brackets  should  be  securely  bolted  to 
the  dash  rail,  so  as  to  ground  the  controller  frame 
independently  of  the  controller  internal  ground, 
thereby    minimizing   the    chances   of   shocking   a 
passenger  should  the  ground  wire  become  loose. 
Before  connecting  the  ground  wire,  the  lamp  test 
should  show  the  controller  frame  to  be  perfectly 
grounded  through  the  dash  rail. 

57.  Note.     On  a  metallic  return  system  there 
is  no  ground  wire,  so  it  is  not  customary  to  consider 
this  feature. 

58.  Remarks.      Locating   defects   in   operating 
controllers   will   be   considered   elsewhere,   but   it 
may  be  said  here: —    An  open-circuit  that  affects 
operation  on  both  ends  of  a  car,  is  not  in  a  controller, 
because  the  two  controllers  are  in  parallel,  and 
parallel  circuits  constitute  independent  paths  for 
current. 


FIG.  16 

If  the  reverse  switch  on  one  end  of  a  car  is  in  a 
certain  position  and  a  motorman,  unaware  of  the 


24  MISCELLANEOUS  TESTS  OF 

condition,  tries  to  start  with  the  other  reverse 
switch  in  the  same  position,  a  fuse  or  breaker  will 
act  as  soon  as  advancement  of  the  controller  cuts 
out  sufficient  resistance,  the  path  of  the  short- 
circuiting  current  being  indicated  in  Fig.  16  by 
means  of  two  old  reverse  switches.  The  short- 
circuit  path  is  shown  by  the  arrow  heads. 


CAR  STARTING  COILS 

OHMIC  RESISTANCE 

59.  Requirements.     The  resistance  of  a  starting 
coil  can  be  measured  on  or  off  the  car,  as  explained 
in  "  Shop  Tests  on  Electric  Car  Equipment,1'  Arts. 
27-30.     The  best  resistance  value  is  governed  by 
smooth  starting  under  average  conditions  of  load 
and  voltage.     A  coil  that  will  start  one  car  satis- 
factorily, will  start  a  heavier  car  sluggishly  and  a 
lighter  one  with  a  jerk.    The  best  test  is  to  install 
a  coil  and  try  it  under  operating  conditions,  and 
note  whether  it  gives  smooth  starts  or  not  and 
whether  it  heats  too  much.    If  parts  of  the  coil  show 
discoloration  after  several  days  of  operation  with 
careful  handling,  the  cross- section  of  the  resistance 
metal  must  be  increased  to  increase  the  current 
carrying  capacity  and  a  greater  length  of  it  must 
then  be  used  to  keep   the  resistance  the   same. 
Starting    coil    resistances    should    be    periodically 
tested  and  defective  sections  renewed.     Properly 
maintained    coils    minimize    abuses    in    controller 
handling  and  permit  the  car  breakers  to  be  set  at 
a  lower  operating  value,  thereby  decreasing  the 
maximum  possible  current  per  car. 

60.  Section  Test.     As  voltage  applied  to  a  series 
circuit  distributes  itself  according  to  the  distribu- 
tion  of   resistance,    the   sectional   distribution   of 
starting  coil  resistance  can  be  determined  with  a 

25 


26  MISCELLANEOUS  TESTS  OF 

voltmeter.  The  sum  of  the  drops  on  the  separate 
sections  should  equal  the  drop  across  the  whole 
coil. 

61.  Directions.  In  applying  a  voltmeter  to 
determine  the  distribution  of  resistance  in  a  starting 
coil,  Pass  a  small  current  through  the  coil,  take  the 
drop  on  the  whole  coil,  then  on  each  section,  then 
on  the  whole  coil  again  to  insure  all  readings 
being  taken  at  the  same  line  voltage.  In  each 
case  write  down  the  reading  and  designate  the 
terminals  from  which  it  was  taken.  Repeat  sets 
of  readings  until  certain  of  a  set  taken  at  the  same 
line  voltage. 

TABLE  II 
Rj-Rg^OO  Volts 
Rj-R-5-64       " 
R2-R3=1S       ' 


Table  II  gives  test  readings  taken  from  a  Wes- 
tinghouse  coil  after  years  of  service.  In  this  test 
an  extra  resistance  of  18  ohms  was  connected  in 
series  with  the  coil,  the  line  voltage  being  495 
volts. 

62.  Note.  The  drop  across,  hence  the  resistance 
of,  the  first  section  exceeds  half  the  total  drop  of 
99  volts.  The  drop  on  section  2  (R2-R3)  exceeds 
half  the  drop  from  R2  to  R5;  and  the  drop  on 
section  3  (R3-R4)  exceeds  naif  the  drop  from  R3 
to  the  end  of  the  coil  —  R5;  and  so  on. 


ELECTRIC  CAR  EQUIPMENT  27 

63.  Empirical  Rule.    Tests  on  numerous  starting 
coils  showed  the  resistance  to  be  so  distributed 
that   notch   2  cut  out  more  than  half  the  total 
resistance  and  each  succeeding  notch  cut  out  a 
little    more    than    half    the    resistance    in    circuit 
immediately  preceding  the  action  of  that  notch. 

64.  Remark.     In  applying  a  voltmeter  to  deter- 
mine the  resistance  distribution  in  a  modern  starting 
coil,  If  the  drop  on  the  first  section  exceeds  half  the 
total  drop  and  the  drop  on  each  succeeding  section 
slightly  exceeds  half  the  remaining  drop,  the  resis- 
tance distribution  may  be  considered  good. 

65.  Example.      A  car  equipped  with  4  motors 
and   K6  controllers    jumped  badly  on    the  sixth 
notch.     What  was  the  trouble? 

66.  Solution.     On  applying  the  voltmeter,  the 
drops  recorded  were  those  of  Table  III.     Noting 


that  the  drop  from  R5  to  R6  was  much  greater 
than  the  drop  on  either  side  of  it,  a  closer  inspec- 
tion was  made  and  the  trouble  was  found  to  be 
due  to  an  open-circuit  in  one  of  the  wires  used 
to  connect  two  parts  of  one  of  the  resistance  units 


28  MISCELLANEOUS  TESTS  OF 

in  parallel,  as  indicated  in  Fig.  17,  where  the  open- 
circuit  is  marked  x. 

TABLE  III 

R1-R7  =  36.0  Volts 

R1-R2  =  17.0 

R2-R3=   8.0 

R3-R4  =   5.0 

R4-R5=    2.5 

R5-R6=    3.5 

R6-R7=    1.5 

R1-R7  =  36.0 

67.  Note.     On  the  older  types  of  controller  that 
had  but  3  or  4  resistance  notches,  the  second  notch 
cut    out   considerable   more   than    half  the   total 
resistance:  thus  on  the  K2  controller,  in  conjunc- 
tion with  a  three-section  starting  coil,  the  second 
notch  cuts  out  two-thirds  of  the  total  resistance 
and  the  third   notch  cuts  out  two-thirds  of  the 
remainder.      On  controllers  employing  from  7  to 
10  resistance  notches,  the  second  notch  can  cut 
out  considerably  less  than  half  the  total  resistance, 
without  any  bad  results. 

68.  Trial  Notching.    This  consists  in  connecting 
the  coil  by  guess,  then  operating  the  car  to  note  its 


ff)  ffa  /?s  R- 

njijmnrmjTJi 


FIG.  18  FIG.  19 

action.  Suppose,  for  example,  that  a  three-section 
coil,  Fig.  18,  thus  connected,  causes  a  bad  jump  on 
the  third  notch.  The  figure  shows  that  Rx  and  R2 
are  too  close  together.  In  some  types  of  coil  this 


ELECTRIC  CAR  EQUIPMENT  29 

would  not  be  so  evident,  as  the  coil  might  be  com- 
posed of  several  frames,  each  containing  several 
sizes  of  resistance  grids.  However,  jumping  on 
the  third  notch  indicates  too  much  resistance 
between  R2  and  R3,  and  too  little  from  R,  to 
R2)  moving  R2  near  to  R3,  as  indicated  by  the  dotted 
line,  would  stop  the  jump  on  the  third  notch  but 
would  tend  to  introduce  it  on  the  fourth,  due  to 
making  resistances  R2  —  R3  and  R3  —  R4  too  nearly 
equal,  the  former  having  been  increased  and  the 
latter  kept  the  same;  this  being  the  case,  then  R3 
could  be  moved  toward  R4,  the  final  connection 
being  indicated  in  Fig.  19.  This  change  might  in 
turn  cause  a  slight  jump  on  the  fourth  notch,  in 
which  case  R2  would  have  to  again  be  shifted  a 
little  and  so  on,  a  satisfactory  arrangement  being 
gotten  only  by  repeated  adjustment  and  trial. 

CHARGED  CONDITIONS 

69.  Insulation  Test.  A  starting  coil  must  have 
good  insulation  from  the  resistance  metal  to  the 
containing  frame  and  from  the  containing  frame 


M 


Voltmeter 


FIG.  20 


to  the  iron  parts  of  the  car;  otherwise,  should  the 
resistance  metal  become  grounded  to  the  frame,  a 
grounded  person  touching  an  exposed  iron  part 


30  MISCELLANEOUS  TESTS  OF 

would  be  liable  to  shock.  The  test  is  best  made 
with  the  connections  of  Fig.  20,  where  T  is  the 
positive  side  of  the  circuit;  V,  the  voltmeter;  G, 
the  negative  side  of  the  circuit  and  I  and  t',  the 
meter  and  ground  test  lines  respectively.  The 
test  can  be  made  as  follows : — 

70.  Directions.     To  test,  with  a  voltmeter,  the 
insulation  resistance  from  the  resistance  metal  to 
the  frame  of  a  starting  coil,  Hold  t  on  the  resis- 
tance metal,  t'  on  the  frame  and  note  the  deflection; 
to  test  the  insulation  from  the  frame  to  a  car  iron, 
hold  t  on  the  frame  and  t'  on  the  car  iron  and  note 
the  deflection. 

71.  Note.     In  neither  case  should  the  insula- 
tion of  an  installed  coil  be  passed  if  the  deflection 
exceeds  250  volts  on  a  500  volt  line,  when  the  under 
side  of  the  car  is  soaking  wet. 

72.  Shock  Test    Assuming  that  50  volts  applied 
to  an  average  man  will  shock  him  sufficiently  to 
cause  him  to  fall:    then  further  assuming  that  a 
60,000  ohm  voltmeter  shows  an  insulation  deflec- 
tion of  250  from  the  frame  to  an  iron  car  part,  and 
that  the  resistance  metal  happens  to  be  grounded 
to  the  containing  frame;    then  under  these  condi- 
tions any  one  touching  the  exposed  iron  car  part  and 
the  ground  at  the  same  time  would  be  shocked. 
As  the  resistance  of  the  person  will  be  in  series  with 
that  of  the  leakage  path  to  the  car  iron,  the  voltage 
will  divide  between  them  in  the  ratio  of  their  resis- 
tances.   Assuming  the  resistance  of  a  man,  includ- 
ing the  imperfect  contacts  that  he  may  make  with 


ELECTRIC  CAR  EQUIPMENT  31 

the  parts,  to  be  5,000  ohms  and  the  leakage  path 
to  measure  60,000  ohms,  the  drop  across  it  will  be 
12  times  that  across  the  man;  the  man,  then, 
would  be  subjected  to  a  voltage  of  one-thirteenth 
of  500  volts  =  39  volts.  Assuming  a  resistance 
value  for  the  human  body  and  knowing  the  value 


ffaiL 

FIG.  21 

of  the  line  voltage  and  the  resistance  of  the  leak- 
age path,  the  voltage  to  which  a  passenger  is  liable 
under  assumed  conditions,  can  be  calculated  as 
follows : — 

73.  Rule.     To  calculate  the  voltage  to  which  a 
person  will  be  liable  on  touching  an  exposed  part 
fed  through  a  leakage  path  of  known  resistance, 
from  a  line  of  known  voltage,  Multiply  the  assumed 
resistance  of  the  human  body  by  the  line  voltage 
and  divide  by  the  sum  of  the  resistances  of  the  body 
and  the  path. 

74.  Example.     A  passenger  shocked  on  alight- 
ing from  a  car  in  motion  was  thrown  and  injured. 
Investigate  conditions  and  determine  the  approxi- 
mate   voltage    of    the    shock,    assuming    a    body 
resistance  of  4,000  ohms. 

75.  Solution.     The  car  was  turned  in  and  repor- 


32  MISCELLANEOUS  TESTS  OF 

ted  as  charged.  Voltmeter  tests  showed  that  a 
live  starting  coil  frame  charged  a  bonnet  stanchion 
which  the  passenger  held  after  touching  the  ground. 
A  voltmeter  test  showed  a  leakage  path  resistance 
of  but  28,000  ohms,  the  maximum  voltage  at  the 
locality  in  which  the  shock  was  received  being  505 
volts. 

4,000  X  500  =  2,000,000 ;  4,000  +  28,000  =  32,000 ; 
and  2,000,000  -J-  32,000  =  62+  volts. 

76.  Note.  The  leakage  path  resistance  can  be 
measured  as  described  in  Art.  40,  P.  51  of  "  Shop 
Tests  on  Electric  Car  Equipment," 


CAR  LIGHTNING  ARRESTERS 

CONNECTION  TESTS 

77.  Conventional  Connection.  A  lightning  arrest- 
er with  a  broken  or  loose  trolley  or  ground  wire 
is  useless  as  protection.  These  connections  should 
be  tested  periodically.  In  Fig.  22,  T-M  is  the  path 
from  the  current  collector  to  the  controller.  The 
arrester,  of  which  a  and  b  are  spark  points,  taps  in 


To  motors 
Sparfrgap 


FIG.  22 

at  x  and  to  ground  at  G.  If  x  is  on  the  car  roof  on 
the  positive  side  of  all  switches  and  circuit  breakers, 
it  will  be  alive  whenever  the  pole  is  on;  but  if  on 
the  controller  trolley  wire,  one  breaker  or  switch, 
if  the  two  are  in  parallel,  or  both,  if  in  series,  must 
be  closed,  before  the  upper  spark  point  of  the 
arrester  is  alive. 

78.  Directions.  To  ascertain  if  the  arrester 
trolley  connection  is  intact,  Ground  one  end  of  a 
lamp  circuit  and  touch  the  other  to  the  upper  spark 
point.  To  ascertain  if  the  lower  spark  point  is 
grounded,  Connect  one  end  of  the  lamp  circuit  to 
trolley  and  touch  the  other  end  to  the  lower  spark 


34  MISCELLANEOUS  TESTS  OF 

point.     In  both  cases,  the  lamps  will  glow  if  con- 
nections are  intact. 

79.  Note.     On     arresters     in    which    the     car 
current  traverses  the  blow-out  coil,  no  trolley  test 
is  required,  for  an  open-circuit  would  prevent  the 
car  from  taking  any  starting  current. 

80.  Actual  Connection.     Fig.  23  is  a  sketch  of 
the  internal  connections  of  a  much  used  type  of 
arrester.     Stretch  of  circuit  T-M  leads  to  the  con- 
troller and  includes  fuse  box  FB ;   the  arrester  tap 


To  Motors     _ 


FIG.  23 

isat#;  the  spark  points  are  a  and  b ;  m,  a  magnetic 
blow-out  coil;  posts  1,  2  and  3  include  a  carbon 
resistance  rod.  A  lightning  discharge  takes  path 
a-6-o-l-2-3-G;  the  trolley  current,  which  follows, 
takes  the  lower  resistance  path  a-6-o-m-2-3-G, 
including  the  blow-out  coil,  which  extinguishes  the 
arc.  A  test  can  be  made  as  follows: — 

81.  Directions.     In  testing  an  arrester  for  con- 
tinuity, the  continuity  of  the  carbon  rod  is  insured 
by  inspection;  with  a  test  circuit,  Test  continuity 
from  0  to  1  and  from  0  to  2. 

82.  Note.     A  break  in  0-1  will  make  the  arrester 
useless,  for  a  lightning  discharge  will  not  traverse 
coil  m.    A  break  in  0-2  will  disable  coil  m,  in  which 


ELECTRIC  CAR  EQUIPMENT  35 

case  a  discharge  would  be  likely  to  destroy  the 
arrester. 

83.  Operating  Test.     The  final  test  for  arresters 
is  to  install  them  where  lightning  discharges  are 
frequent  and  violent,  see  that  they  are  kept  adjusted 
and  inspect  them  after  each  storm  to  note  the 
condition  of  those  that  may  have  operated. 

84.  Arc  Extinguishing  Test.    The  effectiveness 
of  the  blow-out  device  in  extinguishing  arcs,  can 
be  tested  as  follows:  — 

85.  Directions.     To  test  the  arc  extinguishing 
effectiveness  of  an  arrester  blow-out  device,  Connect 
the  arrester  as  in  Fig.  24,  where  K  is  a  circuit- 
breaker  or  switch;    R,  a  resistance  of  one  or  two 

ff         Resistance 
000  -  W 
T       Qr&afrer     R 


FIG.  24 

ohms;  a  and  b,  the  arrester  spark  points;  c,  a 
single  strand  of  flexible  lamp  cord  to  serve  as  a 
fuse.  On  closing  switch  K,  the  melting  of  the  fuse 
establishes  an  arc  that  the  blow-out  should  break. 

86.  Note.     Resistance  R  replaces  the  resistance 
ordinarily   provided   by   the   line   and   the   track 
return,  thereby  limiting  the  short-circuit  to  actual 
working  conditions. 

87.  Air-gap   Adjustment.     Where   an   arrester 
has  an  air-gap,  it  must  be  thinner  than  any  equip- 
ment insulation   to   be   protected,   otherwise  the 
lightning  discharge  is  apt  to  puncture  the  insula- 


36  MISCELLANEOUS  TESTS  OF 

tion  of  some  expensive  device  instead  of  jumping 
the  air-gap.  The  gap  thickness  used  is  0.025  in. 

88.  Directions.     To  test  or  adjust  the  thickness 
of  an  arrester  air-gap,  Make  a  sheet  metal  gage 
0.025  in.  thick  and  of  convenient  size  and  shape  to 
insert  between  the  spark  points.     Apply  the  gage 

k 

F 

FIG.  25  FIG.  26 

as  in  Fig.  25  and  not  canted,  as  in  Fig.  26,  other- 
wise the  real  air-gap  will  be  thicker  than  the 
apparent  one. 

89.  Note.     Some  railway  men  doubt  the  effec- 
tiveness  of   car   arresters,    this   skepticism   being 
based  on  the  failure  of  the  arresters  to  save  equip- 
ment.    Failure  is  as  often  due  to  neglect  as  to 
inherent  unreliability.    One  of  the  writers  twice 
sat  over  arresters  that  operated  effectively   and 
has  no  difficulty  in  recalling  the  occasions. 


CAR  WIRING  CABLES 
PRELIMINARY  CONSIDERATIONS 

90.  Cable;  tests   include   a   preliminary   deter- 
mination of  the  manner  in  which  the  cable  must  be 
tagged  to  have  the  car  respond  correctly  to  the 
indication  of  the  reverse  switches  on  both  ends; 
ringing  out  and  testing  for  insulation  and  crosses. 

91.  Motor  Rotation  Test.     This  test  is  to  deter- 
mine the  direction  of  armature  rotation  for  given 
connections : — 

92.  Directions.     To  ascertain  the  direction  of 
armature  rotation  for  armature  and  field  connec- 
tions of  given  polarity,  Connect  a  field  and  armature 
terminal  together,   ground  one  of  the  remaining 
terminals,  connect  the  other  to  trolley,  close  the 
the  circuit  and  note  the  direction  in  which  the 
armature  rotates,  the  observer  facing  the  commu- 
tator end  of  the  motor. 


FIG.  27 

Thus  Fig.  27  shows  that  when  the  right  hand 
brush-holder    is    positive    the    left    hand    holder 
negative,  the  top  field  lead  positive  and  the  bottom 
37 


206524 


38  MISCELLANEOUS  TESTS  OF 

negative,  the  armature  rotates  in  a  clockwise  direc- 
tion on  this  particular  motor.  In  any  case  the 
direction  of  car  motion  will  be  opposite  to  that  of 
the  top  of  the  armature,  because  the  axle  and  ar- 
mature are  connected  by  gear  and  pinion.  In 
modern  controllers,  the  single  A's  are  positive  and 
the  double  A's  negative,  the  F's  are  positive  and 
the  E's  negative.  Thus  A,,  A2,  Fx  and  F2  are 
positive;  but  AAX,  AA2,  Et  and  E2  or  G  are  nega- 
tive. Only  these  have  to  do  with  direction  of  rota- 
tion. 

93.  Application  of  Data.  Standing  at  the  center 
of  a  single-truck  car  and  looking  toward  either  end, 
the  commutator  will  be  on  the  right.  Viewing  a 
motor  from  the  commutator  end,  for  it  to  move 
the  car  to  the  right  or  forward,  the  top  of  its  arma- 
ture must  move  to  the  left.  As  the  axle  is  to  the 
right,  the  motor  leads  will  probably  be  brought  out 
of  the  frame  on  the  left.  Fig.  27  shows  them  brought 


FIG.  28  FIG.  29 

out  on  the  right;  the  effect  of  such  a  change  is  to 
reverse  the  current  in  the  field  coils  for  given 
connections.  In  Fig.  28,  when  the  top  field  lead 
is  positive,  the  current  around  the  field  is  counter 
clockwise;  on  changing  the  leads  to  the  left  and 


ELECTRIC  CAR  EQUIPMENT 


39 


keeping  the  top  field  lead  positive,  the  current 
around  the  fields  becomes  clockwise  as  in  Fig.  29. 
For  the  top  of  the  armature  to  move  to  the  left, 
then,  the  right  hand  brush-holder  must  be  positive, 
so  that  the  top  field  lead  can  be  kept  positive,  a 
condition  that  lessens  the  liability  of  grounded 
field  parts. 

TAGGING  AND  INSULATION  TEST 

94.  Tagging  the  Cable.  Cable  work  in  detail 
will  be  considered  under  another  heading.  Tagging 
is  but  a  small  part  of  it.  For  a  two-motor  car, 
employing  a  four-  section  starting  coil,  there  will 
be  trolley  and  ground  wires;  five  resistance  wires 
and  seven  motor  wires,  one  field  wire  being  in 
common  with  the  ground  wire.  (On  cars  for  a 
conduit  system,  the  T2  wire  replaces  the  G  wire 
and  there  is  an  extra  E2x  wire  running  from  one 
cutout-switch  to  the  other  making  a  total  of  15 


wires.)  Fig.  30  is  a  sketch  of  a  completed  cable, 
the  two  larger  wires  of  which  are  trolley  and  ground. 
95.  Directions.  To  tag  a  cab1e,  Tag  one  end  of 
each  of  the  larger  wires  T  and  G;  then,  with  a  test 
circuit,  identify  the  other  ends  and  tag  them  the 


40  MISCELLANEOUS  TESTS  OF 

same.  Next,  identify  the  intermediate  taps,  of 
which  there  are  three  on  G  and  one  on  T,  and  tag 
them  the  same  as  their  corresponding  through 
wires.  Next,  assuming  all  remaining  wires  to  be 
of  the  same  size,  tag  them  successively,  on  one  end, 
R!,  R2!  R3,  R4,  R5,  A!  AAX,  Flf  Elt  A2,  AA2,  F2  and  E2. 
Next,  identify  the  opposite  ends  of  each  and  tag 
them  accordingly.  Finally,  identify  the  inter- 
mediate taps  and  tag  them. 

96.  Note.     Knowing  the  location  of  the  starting 
coil  and  the  order  in  which  its  terminals  lie,  the 
resistance  tap  wires  are  brought  out  and  tagged  in 
the  same  order  to  avoid  crossing  the  taps  under  the 
car.    The  motor  cable  terminals,  also,  are  brought 
out  to  be  opposite  the  correct  motor  leads. 

Where  a  number  of  cars  are  to  be  done,  care  in 
tagging  the  first  cable  will  save  much  time  in  con- 
necting the  cars. 

97.  After  the   cable   is   tagged,   the   armature 
wires  on  the  No.  2  end  are  exchanged,  A!  exchang- 
ing places  with  AAt  and  A2  with  AA2.     Unless 
this  is  done,  the  car  will  obey  the  indication  of  the 
reverse  switch  on  one  end  but  not  on  the  other. 
Except  where  the  cable  men  understand  each  other 
well,  it  is  best  to  tag  the  wires  straight  and  cross 
them  afterward;    sometimes  the  wires  are  tagged 
straight  anyhow,   the  crossing  being  left  to  the 
wireman  that  connects  the  controllers. 

98.  Insulation  Test.     This  test,  made  with  a 
lamp  or  bell  circuit,  simply  insures  that  no  wire 
touches   any   other   wire.      On  piped   equipment, 


ELECTRIC  CAR  EQUIPMENT  41 

the  insulation  test  is  made  with  high  voltage  (2,000) 
because  a  wire  is  liable  to  be  snagged  in  drawing  it 
through  the  pipe.  Fig.  31  shows  the  connections 
for  the  test,  the  number  of  lamps  in  series  depend- 
ing on  the  voltage  used.  Test  point  t  is  attached 
to  any  wire  and  tf  touched  to  all  other  wires, 


FIG.  31 

this  test  being  repeated  until  all  wires  have  been 
tested  together.  Where  the  lamps  indicate  a  con- 
tact, the  involved  wires  may  be  found  to  be 
touching  each  other  at  the  ends  of  the  cable. 


CAR  MOTORS 

BRUSH-HOLDER  REQUIREMENTS 

99.  Brush  Spacing.  Brush  spacing  refers  to 
the  distance  apart  of  the  brushes  on  the  commu- 
tator. Thus  in  Fig.  32,  where  a  is  one  brush,  b  the 
other,  c,  the  commutator,  angular  distance  d  is 
a  fixed  quantity  and  must  be  maintained  if  the 


FIG.  32 


FIG.  33 


motor  is  to  operate  sparklessly.  The  commutator 
bars  are  wedge-shaped  and  get  thinner  as  the 
commutator  wears;  as  the  brushes  remain  the 
same  thickness,  the  number  of  bars  between  inside 
brush  edges  is  slightly  less  on  a  worn  commu- 
tator than  on  a  new  one;  but  the  number  of  bars 
between  brush  centers  and  the  angular  distance 
d  do  not  change  if  the  holders  are  correct  in  the 
first  place. 

100.     Radial   Alinement.      As  the  commutator 

wears  or  is  turned  to  smooth  it,  the  feeding  in  of 

the  brushes  must  be  strictly  radial,  that  is,  the 

brush  contact  surfaces  must  move  directly  toward 

42 


ELECTRIC  CAR  EQUIPMENT 


43 


the  center  of  the  commutator.  Fig.  32  indicates 
strictly  radial  brushes;  here  the  long  axes  of  the 
brushes  are  continuations  of  the  radii  drawn  to 
the  centers  of  the  brush  contact  surfaces.  The 
brushes  will  set  square  with  the  commutator  when 
installed  and  will  wear  square  on  the  ends.  Fig. 
33  indicates  brushes  the  contact  surfaces  of  which 
follow  commutator  wear  radially,  but  the  axes 
of  which  are  not  radial,  the  ends  being  beveled 
to  give  greater  contact  surface  without  increasing 
the  thickness  of  the  brush.  The  requirement  of 
such  a  brush  is  that  the  wearing  surface  shall  feed 
radially  although  the  brush  does  not. 

101.  Symmetry  of  Set.  The  brush-holder  must 
primarily  hold  and  maintain  the  brushes  sym- 
metrical in  regard  to  a  certain  line  passing  through 
the  center  of  the  commutator.  On  most  surface 


FIG.  34  FIG.  35 

car  motors  line  xy  Fig.  34,  passing  through  the 
centers  of  contact  of  the  brushes,  is  horizontal 
if  the  motor  sits  level;  in  such  a  case,  the  line  of 
symmetry  is  vertical  radius  dc.  On  some  of  the 
larger  motors  used  in  high  speed  service,  the  motor 


44  MISCELLANEOUS  TESTS  OF 

hand  hole  covers  are  set  at  an  angle  so  that  brush 
inspection  and  renewals  can  be  made  from  the 
under  side  of  the  car  without  lifting  trap-doors ;  the 
line  of  symmetry  is  not  then  the  vertical  radius, 
but  some  other  radius  the  deflection  of  which 
depends  on  the  angle  of  displacement  of  the  hand 
holecover.  In  any  case,  angles  acd  and  bed  must 
be  equal  or  the  brushes  will  spark  in  one  or  the 
other  direction  of  rotation. 

BRUSH-HOLDER  IRREGULARITIES 

102.  Types  of  Holder.  Brush-holder  riggings 
are  of  either  the  independent  type  or  the  yoke  type. 
In  the  former,  the  two  holders  are  not  mechanically 
connected: — most  Westinghouse  railway  holders 
are  of  this  type.  In  the  yoke  type,  the  two  holders 
are  supported  by  a  wooden  yoke: — most  of  the 
older  holders  of  the  General  Electric  Company  are 
of  this  type.  Most  of  the  irregularities  of  the 
independent  type  are  incident  to  carelessness  or 
ignorance  in  repairs  or  installation: — The  holder 
seats  in  the  motor  frame  are  babbitted  with  a  jig, 
so  that  a  correct  holder  properly  installed  cannot 
set  the  brushes  wrong;  but  if  holder  seats  are  rebab- 
bitted  with  a  homemade  jig  that  is  in  error,  or 
if  the  holders  be  made  of  castings  of  varying  shrink- 
ages and,  therefore,  of  uncertain  dimensions,  or 
if  in  installing  the  holder  no  care  is  taken  that  the 
holder  guide  surfaces  register  flush  with  the  corres- 
ponding frame  seats,  the  brush  set  is  apt  to  be 
wrong.  The  yoke  type  is  liable  to  the  same  irregu- 


ELECTRIC  CAR  EQUIPMENT  45 

larities  and  in  addition  endless  trouble  can  be 
started  by  using  untreated,  badly  seasoned  wood 
or  yoke  brackets  of  different  heights. 

103.  Errors  of  Setting.     Wrong  brush  set  may 
be  due  to  one  or  more  of  several  conditions  that 
will  now  be  considered, 

104.  Wrong    Brush    Spacing    means    brushes 
too  close  together  or  too  far  apart;  in  either  case 
there  will  be   sparking,   but  more   in   the   former 
case  than  in  the  latter.    One  brush  may  be  in  its 
right  position,  Fig.  36,  but  the  other  too  far  one  way 
or  the  other : — the  displaced  brush  will  spark. 


FIG.  36 


FIG.  37 


105.  Lack  of  Symmetry,  that  is,  the  brushes 
correctly  spaced,  so  far  as  count  is  concerned,  but 
both  holders  too  far  around  in  one  direction  or 
the  other,  Fig.  37,  will  cause  sparking  in  one  direc- 
tion of  rotation,  but  not  in  the  other,  because  in 
one     direction     armature     reaction     reduces    the 
sparking,  but  in  the  other  aggravates  it. 

106.  Lack  of  Radial  Alinement,  even  with  cor- 
rect spacing  and  symmetry,  will  cause  initial  spark- 
ing, unless  the  brushes  are  sandpapered  to  fit  the 


46  MISCELLANEOUS  TESTS  OF 

commutator,  and  conditions  will  get  worse  with 
time.  In  Fig.  38,  the  brush  axes  point  at  c' — above 
the  commutator  center,  so  that  wear  will  bring 


FIG.  38  FIG.  39 

them  closer  together  and  out  of  set.  In  Fig.  39, 
the  brush  axes  point  at  c" — below  the  commutator 
center,  so  that  commutator  wear  will  force  them 
further  apart — a  bad  enough  condition,  but  not  as 
bad  as  the  first. 

107.     Wrong  Height  of  Bracket  raises  or  lowers 
the  holders  vertically,  according  as  the  bracket  is 

A 


FIG.  40 

too  short  or  too  long  (see  Fig.  40).  With  a  short 
bracket,  the  brush  axes  will  point  above  center 
and  the  brushes  will  close  in  with  commutator 
wear.  With  a  long  bracket,  the  brush  axes  will 


ELECTRIC  CAR  EQUIPMENT 


47 


point  below  center  and  the  set  will  spread  with 
commutator  wear.  Defect  in  radial  alinement 
differs  from  a  bracket  defect  in  that  the  former  may 
correctly  space  the  brushes  initially,  while  the  latter 
starts  them  off  with  incorrect  spacing  and  main- 
tains the  condition. 

108.  Canted  Brushes  refers  to  the  condition 
illustrated  in  Fig.  41  (a),  in  which  the  brush  is 
shown  resting  on  one  end  corner.  Under  this 
condition  the  brush  contact  surfaces  will  wear  to 
the  shape  indicated  in  Fig.  41  (b).  On  the  inde- 


FIG.  41 

pendent  type  of  holder,  this  may  be  due  to  insu- 
lating washers  of  uneven  thickness  or  to  foreign 
matter  behind  them.  If  the  brushes  in  both 
holders  of  the  yoke  type  wear  in  this  way,  indica- 
tions point  to  irregularity  in  the  setting  of  the  yoke 
itself,  but  it  is  possible  for  both  holders  to  be  in 
fault. 

109.  Wear  in  Armature  Bearings  lowers  the 
commutator  bodily,  thereby  causing  holders,  other- 
wise all  right,  to  set  the  brushes  too  close  together, 


48  MISCELLANEOUS  TESTS  OF 

as  shown  in  Fig.  42.  The  error  may  be  small,  but 
where  the  bearings  are  babbitted  above  center  to 
increase  the  safe  wear  and  to  decrease  the  frequency 
of  clearance  inspections,  the  error,  in  conjunction 
with  other  errors,  may  be  considerable.  As  motors 


FIG.  42 

spark  less  with  brushes  too  far  apart  than  with 
them  too  close  together,  it  might  be  well  to  so 
design  holder  riggings  as  to  initially  set  the  brushes 
a  little  too  far  apart,  to  allow  for  the  effect  of  bear- 
ing wear. 

110.  Brush    Pressure.     By    brush    pressure    is 
meant  the  force  with  which  the  brush  is  pressed 
down  by  the  brush-holder  spring. 

111.  Pressure  Requirements  are  varied;    more 
pressure  is  needed  on  rough  track  or  at  high  speed 
than   on    smooth    track   or   at   low   speed;     some 
qualities  of  brush  require  more  pressure  than  others. 
With  deficient  pressure,   rough  track  or  commu- 
tator   will    cause    the   brushes   to    jump,    thereby 
producing  bad  sparking  and  liability  to  flash  over. 
Excessive  pressure  subjects  both  commutator  and 
brushes  to  excessive  wear.     Between  these  limits 


ELECTRIC  CAR  EQUIPMENT  49 

wide  variations  exist,  even  on  motors  from  the 
factory. 

To  reduce  pressure  comparisons  to  a  common 
basis,  the  pressures  must  be  expressed  as  so 
many  units  of  force  per  unit  of  contact  surface. 
The  units  used  in  this  country  are  pounds  or  ounces 
per  square  inch.  The  brush  pressures  on  surface 
car  motors  vary  from  2  to  6  Ib.  per  square  inch. 

112.  Pressure  Tests  consist  in  actually  applying 
a  scale  to  determine  the  total  brush  pressure  on 
the  commutator.  In  applying  the  scale,  the  read- 
ing must  be  taken  when  the  scale  and  brush  axes 
are  in  line  as  in  Fig.  43,  where  the  correct  pull  is 


BHSpring 

liK 

\8rvsh 
Co'm 

FIG.  43 

indicated  along  line  ac;  a  reading  taken  in  any  other 
direction,  such  as  ab  or  ad,  will  not  be  a  true  one. 
If  the  pressures  are  to  be  measured  on  installed 
holders,  and  the  motor  shells  prevent  a  direct  pull 
on  the  scale,  a  smaller  scale  must  be  obtained  or 
a  rigging  similar  to  that  of  Fig.  44  used.  Here  the 
scale  connects  to  a  lever  at  its  middle  point,  the 
end  o  engaging  the  brush  finger  as  near  to  the  brush 


50  MISCELLANEOUS  TESTS  OF 

as  practicable.    The  test  is  applied  and  calculated 
as  follows: — 

113.  Directions.     To  test  brush  pressure  with 
a  spring  scale,  Hold  the  scale  in  one  hand,  the  end 
x,  of  the  lever  in  the  other;    pull  on  the  scale  and 
push  on  the  lever,  keeping  the  axis  of  the  scale  at 
right  angles  to  that  of  the  lever;  just  as  the  brush 
finger  leaves  the  brush,  read  the  scale.    To  get  the 
total  brush  pressure  in  pounds,  divide  the  scale 
reading  by  two. 

114.  Note.     Were    the    scale    applied    directly 
to  the  finger,  the  reading  would  be  direct;   but  as 
the  pull  is  applied  to  the  middle  of  a  lever,  the  ends 
of  which  are  supported  by  two  equal  pulls,  the  scale 
reading  must  be  divided  by  two. 

115.  Expressing  the  Pressure  is  now  a  matter 
of    determining    the    area    of    the    brush    contact 
surface  in  sq.  in.,  then  dividing  the  total  pressure 
by  the  area  to  get  the  pressure  per  sq.  in.     The 
surface  area  can  be  calculated  as  follows : 

116.  Ride.     To  get  the  area  of  a  brush  contact 
surface  in  square  inches,  Multiply  the  length  and 
breadth  of  the  contact  surface  in  inches;  the  result 
will  be  the  contact  area  in  square  inches. 

117.  Example.     The  contact  area  of  a  G.E.57 
brush  measures  f  in.  by  If  in.     Find  the  contact 
surface  area  in  square  inches. 

118.  Solution.     |Xlf  =  f  Xf=l&  sq.  in. 

119.  Note.     Except  where  the  contact  surface 
is  beveled,  as  in  the  case  of  the  G.E.800  brush,  the 


ELECTRIC  CAR  EQUIPMENT  51 

brush  width,  multiplied  by  its  thickness,  gives  the 
area  of  the  contact  surface. 

Having  the  area  of  the  contact  surface  and  the 
total  brush  pressure,  the  pressure  per  square  inch 
is  calculated  from  the  following: 

120.  Rule.     To    get    the    brush    pressure    per 
square  inch,   Divide  the  surface  contact  area  in 
square  inches  by  the  total  pressure  in  pounds. 

121.  Example.     The  contact  surface  area  of  a 
G.E.57  brush  is   1-^j-  sq.  in.  and  the  total  pressure 
9  Ib.    What  is  the  brush  pressure  per  square  inch? 

122.  Solution.   9-i-l&-9-*-M  =  9Xfi-W- 
8.23  Ib.  per  sq.  in. 

MISCELLANEOUS  BRUSH  TOPICS 

123.  To  conclude  the  brush-holder  subject,  dis- 
tance from  commutator,  counting  off  brushes  and 
the  importance  of  brush-holder  maintenance  will 
be  considered. 

124.  Distance  from  Commutator  refers  to  the 
clearance  between  the  lower  end  of  the  holders  and 


Gage 


&H+ 

FIG.  44          FIG.  45  FIG.  46 

the  commutator.  If  this  distance  is  excessive,  the 
brushes  are  apt  to  shift  positions  when  the  direc- 
tion of  motion  of  the  car  is  reversed,  and  develop 


52  MISCELLANEOUS  TESTS  OF 

two  wearing  surfaces,  as  indicated  in  Fig.  45. 
The  same  condition  will  obtain  if  the  brush  is  too 
thin  or  the  brush-way  too  large.  If  the  holders  sit 
too  close  to  the  commutator,  dust  and  oil  are  apt 
to  gum  up  the  clearance  and  cause  sparking.  The 
proper  clearance  is  about  y\  in.  and  this  clearance 
should  be  insured  by  applying  a  gage  as  in  Fig.  46, 
the  gage  being  tapered  a  little  to  facilitate  with- 
drawing it. 

125.  Note.     To  insure  uniform  dimensions  of 
brushes,    they    should    be    passed    through    limit 
gages  and  the  extra  thin  and  thick  ones  rejected. 
In    installing    brushes,    they    should    be    inserted 
from  both  ends  to  see  that  one  end  is  not  thicker 
than  the  other,  because  if  this  is  the  case  and  the 
brush  is  inserted  thin  end  first,  it  will  stick  when 
the  thick  part  reaches  the  brush  way  and  trouble 
will  follow. 

126.  Counting  Off  Brushes  consists  in  counting 
the  number  of  commutator  bars  included  in  the 
brush  spacing.    Counting  bars  is  easier  than  meas- 
uring distance  in  a  hot  motor.     A  draughtsman 
will  count  brush  set  from  the  center  of  contact 
of  one  brush  to  the  center  of  contact  of  the  other, 
because  he  has  the  drawing  where  he  can  get  at 
it;    the  car-house-man,  however,  can  not  conveni- 
ently locate  the  centers  of  contact,  because  shadows 
and  the  lower  end  of  the  holders  obscure  them;   so 
he  counts  the  bars  included  between  the  inside 
edges   of   the   brushes,   as  indicated   in    Fig.    47, 
where  both  the  center  to  center  'and  inside  counts 


ELECTRIC  CAR  EQUIPMENT  53 

are  shown.  Knowing  the  number  of  commutator 
bars  and  the  number  of  motor  poles,  the  center  to 
center  count  is  gotten  from  the  following  rule: 


FIG.  47 

127.  Rule.     To  get  the  center  to  center  count 
of  the  brushes  on  a  railway  motor  from  the  number 
of  commutator,  bars  and  motor  poles,  Divide  the 
number  of    commutator  bars    by  the  number  of 
motor  poles. 

128.  Example.     A  Westinghouse  No.  101  motor 
has  111  commutator  bars  and  4  motor  poles.    What 
is  the  center  to  center  brush  count? 

129.  Solution.     111+4  =  27  f  bars. 


FIG.  48 

130.     Deriving  the  Inside  Edge  Count  from  the 
center  to  center  count  requires  that  one  of  the 


54  MISCELLANEOUS  TESTS  OF 

brushes  be  applied  to  a  commutator,  as  indicated 
in  Fig.  48,  to  determine  how  many  bars  are  spanned 
by  the  thickness  of  a  brush.  With  this  information, 
the  inside  count  can  be  derived  from  the  center  to 
center  count,  by  the  following  rule: — 

131.  Rule.     To  get  the  inside  brush  count  of  a 
railway  motor  from  its  center  to   center  count, 
Subtract  from  the  center  to  center  count  the  num- 
ber of  commutator  bars  spanned  by  the  thickness 
of  one  brush. 

132.  Example.     The  center  to  center  count  of 
a  Westinghouse  No.   101  motor  is  27f  bars;    the 
brush  spans    If  bars.      Wanted,  the  inside  edge 
count. 

133.  Solution.     27f  bars  -  If  bars = 26  bars. 

134.  The  Importance  of  Brush-holder  Mainte- 
nance   can    not    be    exaggerated.       Considerable 
space  has  been  given  to  brush-holders  and  their 
irregularities  and  more  could  be  devoted  to  the 
subject  if  it  could  be  included  in  a  testing  book  of 
limited  scope: — armature  endplay,  crooked  holders, 
maintenance  and  desirability  of  shunts,  freedom  of 
moving  parts,  etc.,  could  well  be  discussed.     The 
only  way  to  maintain  brush-holders  and  parts  is 
with  suitable  jigs  and   efficient   inspection.      The 
introduction  of  jigs  on  a  large  road  reduced  the 
number  of  brush-holder  repairmen  from  4  to  1 ;  this 
represented  but  a  small  economy  as  compared  with 
the  saving  in  the  handling  and  repair  of  other 
equipment  parts  affected  by  sparking  due  to  faulty 
brush-holder    conditions.      This    device    is    more 


ELECTRIC  CAR  EQUIPMENT  55 

abused  and  neglected  through  ignorance,  indiffer- 
ence and  carelessness  than  other  parts  able  to  take 
care  of  themselves.  Did  brush-holder  irregularities 
affect  only  the  holders,  overlooking  their  welfare 
would  not  be  so  serious;  but  when  one  realizes 
that  a  faulty  holder  may  burn  a  string-band, 
loosen  the  head,  break  a  band- wire  and  either  burn 
out  the  armatuie  or  grind  it  to  a  condition  of  use- 
lessness,  or  both,  the  impression  is  gained  that  this 
important  device  should  be  made  and  maintained 
with  care  rather  than  with  "licks  and  no  promises." 

MOTOR  INSULATION  TESTS 

135.  Armature  Insulation.     To  test  the  insula- 
tion of  an  armature  on  the  floor,  use  the  connec- 
tions of  Figs.  36-37,  "Shop  Tests  on  Electric  Car 
Equipment."     For  an  installed  armature,  the  same 
connections  are  used,  but  the  motor  brushes  must 
be  drawn,  otherwise  it  will  not  be  known  whether 
a  possible  ground  is  on  the  armature  or  on  some 
connected  device. 

136.  Field  Coil  Insulation.    On  uninstalled  field 
coils  devoid  of  containing  shells,  there  is  no  sur- 
rounding metal  to  which  insulation  can  be  tested; 
if  such  a  coil  has  been  grounded  it  will  show  it. 
If  the  coil  is  installed  or  has  a  containing  shell, 
the   connections  referred  to  in  Art.    135   can  be 
applied  as  follows: — 

137.  Directions.     To  test  field  coil  insulation 
in  the  motor,  Disconnect  the  field  leads  and  axle 
jumper  and  test  to  find  in  which  half  the  fault  lies; 


56  MISCELLANEOUS  TESTS  OF 

the  faulty  pair  located,  inspect  to  see  if  the  trouble 
may  be  a  terminal  or  connecting  jumper  that  can  be 
fixed  without  opening  the  motor ;  if  on  opening  the 
motor  the  fault  is  not  evident,  separate  the  field  coils 
and  test  them  separately  to  locate  the  fault}7  one. 

138.  Brush-holder  Insulation.     With  the  ordin- 
ary lamp  test  circuit,  brush-holder  insulation  can 
be  tested  as  follows : — 

139.  Directions.     To  test  brush-holder  insula- 
tion, Draw  the  brushes,  disconnect  the  brush  leads 
and  test  between  holders  and  from  each  holder  to 
the  motor  frame. 

140.  Note.    Complete  carbonization  of  the  under 
side  of  a  yoke  may  exist,  in  which  case  it  cannot  be 
seen  from  above  but  can  be  felt  with  the  hand. 

MOTOR  CIRCUIT  TESTS 

•141.  Open-circuited  Field  Coil.  As  a  2-motor  car 
with  an  open-circuited  field  coil  cannot  start  on  a 
series  notch,  the  faulty  motor  must  be  located  either 
by  throwing  the  controller  to  parallel  and  noting 
which  motor  works,  or  by  trying  the  motors  one  at 
a  time.  Inspection  may  reveal  a  disconnected  lead 
or  axle  jumper;  if  not,  the  bell  circuit  test  can  be 
applied  as  follows: — 

142.  Directions.  To  test  for  open-circuit  field 
with  a  bell  circuit,  Disconnect  the  field  leads  and 
see  if  the  bell  will  ring  through  from  one  lead  to 
the  other;  if  not,  disconnect  the  jumper  and  test 
top  and  bottom  pairs  separately;  if  inspection 
shows  that  the  motor  most  be  opened,  do  so  and 


ELECTRIC  CAR  EQUIPMENT  57 

test  one  field  coil  at  a  time  until  the  faulty  one  is 
located. 

143.  Open-circuit  and  Grounded  Coil.  A  special 
case  of  open-circuit  field  coil  is  where  a  connecting 
wire  burns  off  and  welds  to  the  frame,  as  indicated 
in  Fig.  49.  If  on  motor  No.  2,  the  car  will  operate, 
but  the  faulty  motor  will  spark.  A  bell  circuit 


FIG.  49 

applied  to  F2  and  E,  would  indicate  an  open- 
circuit,  because  a  bell  circuit  has  no  ground  con- 
nection. A  lamp  test  would  not  indicate  an  open- 
circuit  unless  the  ground  end  happened  to  be  applied 
to  F2  and  the  trolley  end  to  E2;  with  the  trolley 
applied  to  F2,  a  ground  would  be  indicated.  On 
getting  an  open-circuit  indication  with  t  on  E2  and 
a  ground  indication  with  t  on  F2,  the  true  condi- 
tion would  be  suspected.  Combination  faults, 
consisting  of  two  or  more  faults,  give  much  trouble. 
144.  Open-circuit  Armature  Test  (first  method). 
From  brush  to  brush,  a  railway  motor  armature 
has  two  paths,  so  that  an  open-circuit  in  one  does 
not  open  the  circuit.  One  symptom  of  such  a 
fault  is  a  flash  around  the  commutator  when  the 
car  is  run  on  both  motors  or  is  run  down  hill  on  the 


58  MISCELLANEOUS  TESTS  OF 

faulty  one.  On  a  level,  the  motor  will  start  if  the 
armature  happens  to  be  in  a  favorable  position 
when  the  current  is  applied,  but  will  tend  to  act 
in  impulses. 

145.  Open-circuit      Armature      Test      (second 
method).     A  direct  test  for  armature  open-circuit 
is  to  measure  its  resistance  by  one  of  the  methods 
given  in  "Shop  Tests  on  Electric  Car  Equipment." 
From    brush    to    brush,    an    open-circuit    railway 
armature  will  measure  twice  its  normal  value. 

146.  Open-circuit  Armature  Test  (third  method) . 
A  test  for  open-curcuit  in  an  armature  can  be  made 
with  a  voltmeter  as  follows: — 

147.  Directions.     To  test  an  installed  armature 
for  open-circuits,  with  a  voltmeter,   Connect  the 


FIG.  50 

field-winding  of  the  faulty  motor  in  series  with 
that  of  the  good  motor,  as  indicated  in  Fig.  50,  so 
that  when  the  car  is  operated  the  field  of  the  faulty 
motor  becomes  separately  excited.  Next,  hold  the 
test  lines  from  a  voltmeter  on  the  brush-holders  of 
the  suspected  armature  and  note  the  action  of  the 
voltmeter  needle  when  the  car  is  operated: — with 
an  open-circuit  in  the  armature,  the  voltmeter 
needle  will  wave  to  and  fro. 


ELECTRIC  CAR  EQUIPMENT  59 

148.  Open-circuit  Armature  Test  (fourth 
method).  Fig.  51,  a  diagrammatic  sketch  of  a  ring 
winding,  shows  that  a  single  open-circuit,  as  in- 
dicated at  x  does  not  divide  the  winding  into  two 
isolated  sections,  but  that  if  another  open-circuit, 
as  indicated  at  y,  be  created,  the  winding  is  divided 
into  two  sections  that  will  not  ring  up  together, 


FIG.  51 

when  one  test  point  of  a  bell  circuit  is  touched  to 
Dne  section  and  the  other  to  the  other  section  of  the 
winding.  An  uninstalled,  suspected  armature  can, 
then.be  treated  for  an  open-circuit  as  follows: — 

149.  Directions.    To  test  an  armature  for  open- 
circuit,   Create   an   open-circuit  by   disconnecting 
Dne  coil  lead;  then,  holding  one  test  point  anywhere 
Dn  the  commutator,   pass  the  other  around  the 
commutator: — If    a    faulty     open-circuit    exists, 
there  will  be  certain  bars  on  which  the  test  lamps 
will  fail  to  glow  when  the  free  test  point  is  applied 
to  those  bars. 

150.  Short-circuited  Field  Coils.     If  the  field 
coil  terminals  can  be  bared,  or  if  the  voltmeter 
test  lines  are  provided  with  sharp  awls  with  which 


60  MISCELLANEOUS  TESTS  OF 

to  pierce  their  insulation,  a  faulty  field  coil  can  be 
located  with  a  voltmeter  as  follows: — 

151.  Directions.     To    locate    a    short-circuited 
field    coil    with    a    voltmeter,    Connect    an    extra 
resistance  of  20  or  25  ohms  in  series  with  the  motor 
circuit,  set  the  brake,   pass  a  current   and  take 
the  drop  on  each  coil  with  a  low  reading  voltmeter ; 
a  faulty  coil  will  give  a  lower  drop  than  a  standard 
coil. 

152.  Note.     Should  all  coils  give  the  same  drop, 
all  are  either  good  or  are  equally  bad;  to  ascer- 
tain which,  Connect  a  standard  coil  in  series  with 
them  and  compare  their  drops  with  that  gotten  on 
the  standard  coil  with  the  same  current. 

153.  Short-circuited  Armature.     When  the  car 
is  run  on  both  motors,  the  short-circuited  armature 
will   operate  in  jerks;    this   action   is  intensified 
by  running  the  car  down  hill  on  the  faulty  motor 
alone;  also,  one  or  more  coils  will  heat  much  more 
than  others.     Even  if  the  fault  includes  but  little 
of  the  winding,  if  a  knife  be  held  near  the  head  of 
the  armature  while  taking  current  with  the  car  in 
motion,  the  knife  will  pulsate  in  a  manner  quite 
distinguishable  from  the  more  rapid  vibrations  due 
to  the  field  magnetism  whipping  from  one  tooth  to 
the  next. 

154.  Grounded  Armature.     A  grounded  arma- 
ture acts  similarly  to  a  short-circuited  one,  but 
tends  more  violently  to  lock  in  certain  positions  of 
its  rotation.     A  ground  on  armature  No.    1  will 
prevent  starting  with  current,  unless  the  armature 


ELECTRIC  CAR  EQUIPMENT  01 

happens  to  lie  in  a  position  where  the  effect  of 
the  fault  is  a  minimum;  in  this  case,  the  car  will 
move  a  little  and  stop,  blowing  a  fuse  or  breaker, 
should  the  controller  be  advanced  sufficiently  far. 
With  the  ground  on  armature  No.  2,  the  car  will 
operate  in  series  on  No.  1,  but  the  faulty 
armature  will  turn  in  jerks  and  the  fuse  will  blow 
on  a  parallel  notch. 

FIELD  COIL  POLARITY  TESTS 

155.  Nail  Test.    The  nail  method  of  testing  the 
polarity  of  installed  field  coils  is  given  in  "Shop 
Tests  on  Electric  Car  Equipment,"  Art.  72,  p.  86, 
and  need  not  be  repeated  here. 

156.  Compass  Test  (first  method).     Owing  to 
magnetic   leakage,   a   compass   can   be   externally 
applied  to  determine  if  installed  fields  are  properly 
connected.     Fig.  52  is  a  section  through  the  poles 


FIG.  52 

of  a  motor  and  shows  the  internal  poles,  each  with 
its  external  pole  due  to  magnetic  leakage  in  direc- 
tions indicated  by  the  dotted  lines.  With  correctly 
connected  coils,  the  internal  and  external  poles 


62  MISCELLANEOUS  TESTS  OF 

will  alternate  in  polarity.  With  an  ordinary  pocket 
compass,  that  costs  50  cents,  the  test  can  be  made 
as  follows: — 

157.  Directions.      To    test    field    coil    polarity 
externally  and  with  a  compass,  Connect  a  resistance 
of  20  or  25  ohms  in  series  with  the  motor  circuit, 
set  the  brake  and  block  the  car- wheels;    pass  the 
compass    around    the   motor:     with    proper    field 
connections  the  needle  will  reverse  at  each  pole. 
If  3  poles  are  alike,  the  middle  one  holds  a  wrongly 
connected  coil;   if  there  are  like  pairs  on  a  side  or 
above  and  below  one  pole  of  each  pair  holds  a 
wrongly  connected  field  coil. 

158.  Note.     Some  skill  is  at  first  required  to 
keep  the  compass  needle  from  sticking,  but  this  is 
soon  overcome. 

159.  Note.     If  the  motor  is  first  subjected  to 
full  load  current  while  standing,  the  current  being 
then   thrown  off,  the  test  can  be  made  without 
current,  owing  to  strong  residual  magnetism. 

160.  Compass  Test  (Second  Method).     Bought 
field  coils  may  come  wound  in  the  wrong  direction 
or  with  the  ends  connected  to  the  wrong  lugs; 
such  coils  sent  out  and  installed  bring  on  a  lot  of 
trouble  before  the  cause  is  suspected.    Electrically, 
the  result  is  the  same  as  connecting  the  coils  wrongly 
in  a  motor,  but  the  fault  is  worse  because  it  is  not 
evident  to  inspection.     In  modern  motors  all  field 
coils  are  alike  in  like  motors.     All  standard  coils 
being   alike,   uninstalled   coils   of   wrong   polarity 
can  be  detected  by  the  following  test: — 


ELECTRIC  CAR  EQUIPMENT  63 

161.  Directions.  To  test  the  polarity  of  unin- 
stalled  field  coils  with  a  compass,  Arrange  on  the 
floor  and  connect  in  series  a  standard  coil  and  the 
coils  to  be  tested,  all  being  similarly  placed.  On 
passing  current  and  moving  the  compass  before 

Resistance 

o WVW 


l^^     Stand  Cod   TesFZoci 


FIG.  53 

the  coils  from  one  to  the  other,  the  needle  will 
reverse  in  front  of  any  coil  of  wrong  polarity. 
The  arrangement  of  coils  is  indicated  in  Fig.  53. 

CARBONIZED  FIELD  COILS 

162.  Introductory  Remarks.    It  is  easy  to  devise 
a  test  to  indicate  a  bad  coil  or  a  perfect  one,  but 
intermediate  stages  are  hard  to  indicate  with  cer- 
tainty without  inspection. 

163.  Resistance  Test.     A  fairly  well  baked  coil 
can  be  detected  by  measuring  its  resistance.     In 
measuring  installed  coils,  the  pole-pieces  must  be 
drawn  tight  to  compress  the  coil  and  bring  its 
convolutions  together  as  they  are  when  expanded 
by  heat  in  service.     Often,  owing  to  shrinkage  of 
the  field  insulation,  this  cannot  be  done  without 
loosening  the  pole  bolts  and  slipping   split   insula- 
ting washers  behind  the  coils  to  take  up  the  clear- 
ance.    In  bench  testing,  metal  clamps  must  be 


64  MISCELLANEOUS  TESTS  OF 

made,  Fig.  54,  to  hold  the  coils  while  compressing 
them  in  a  vise.  Their  resistance  is  measured 
while  they  are  under  compression.  Any  coil 
measuring  5  per  cent,  less  than  standard,  is  set  aside 
to  be  inspected.  The  outer  layers  may  be  normal 
and  the  inner  ones  browned;  or  the  outer  layers 


FIG.  54 


FIG.  55 


may  be  light  brown,  too  good  to  scrap,  and  the 
inner  ones  what  the  winder  calls  "rotten."  The 
outer  layers  are  exposed  by  removing  the  outer 
insulation;  but  to  inspect  the  inner  layers,  the 
coil  must  be  carefully  opened. 

164.  Combination    Test.     The    resistance    test 
in  conjunction  with  a  voltmeter  test,  now  to  be 
described,  is  used  for  acquiring  data  sufficient  to 
decide  between  a  good  coil  and  a  bad  one,  and 
without    ripping    the    coil    apart    for    inspection. 
The  combination  test  is  conducted  as  follows: — 

165.  Directions.      To    apply    the    combination 
data  test  to  field  coils,  Tag  each  coil  with  a  number 
and  pile  them  with  No.  1  on  top.     One  at  a  time 
and  with  the  same  current,  take  the  drops  on  each 


ELECTRIC  CAR  EQUIPMENT 


65 


coil,  carefully  noting  the  drop  opposite  the  number 
of  the  coil  that  produced  it;  the  drops  on  all  coils 
are  then  compared  with  the  drop  on  a  standard 
coil  at  the  same  current;  next,  remove  the  outside 
insulation  being  careful  to  replace  any  tags  that 
may  be  torn  off.  Pull  out  the  middle  wire  of  the 
wide  side  of  each  coil,  as  indicated  in  Fig.  55,  and 
cut  it;  this  divides  the  coil  into  2  parts,  the  turns 
of  which  lie  close  together  in  the  center,  where 
carbonization  is  most  intense.  Again  place  the 
coils  under  compression  and,  with  a  voltmeter, 
get  the  insulation  deflection  between  ends  a  and  b, 
in  each  case  writing  the  deflection  opposite  the 
number  of  the  coil  from  which  it  was  gotten.  Next, 
pick  from  the  list  pairs  of  coils  that  have  given 
the  same  drop  and  deflection  and  also  all  coils 
the  drops  and  deflections  of  which,  could  not  be 
paired,  open  the  coils,  inspect  them,  and,  in  a 
fourth  column,  note  the  condition  of  the  worst  part 
of  the  coil,  in  each  case  being  careful  not  to  put  the 
condition  of  one  coil  down  on  the  sheet  opposite 
the  number  of  another  coil. 

TABLE  IV 


Coil  No. 

Drop 

Deflec. 

Remarks 

1 

10 

200 

Slightly  browned  but 

tough. 

2 

6 

450 

Almost  black  and  very 

crumbly. 

3 

1 

500 

.  Rotten. 

4 

11 

10 

Perfect. 

5 

9 

250 

Dark  straw,  crumbly. 

66  MISCELLANEOUS  TESTS  OF 

166.  Record  of  Test.  Table  IV  shows  the  method 
of  tabulating  the  readings  and  making  the  notes. 
On  comparing  the  resistance  drops  in  the  second 
column  with  the  insulation  deflections  in  the  third 
column,  it  will  be  noted  that  a  low  drop  corresponds 
to  a  high  deflection  and  vice  versa,  because  a  low 
drop  means  poor  insulation  and  so  does  a  high 
deflection.     Some  coils  may  show  a  low  drop  and 
no  deflection;    in  such  a  case  investigation  will 
show  that  the  coil  either  is  short  on  turns  or  is 
wound  with  too  large  a  wire.    All  coils  proven  to  be 
reclaimable,canbefixed,if  they  have  heen  handled 
carefully,  the  cut  wire  being  spliced  with  a  copper 
sleeve.     After  the  desired  information  has  been 
gotten  for  each  type  of  coil  in  service,  the  test  record 
is  kept  for  reference;   after  a  perfect  line  has  been 
gotten  on  the  relation  between  the  resistance  of 
the  coil  and  its  condition,  as  revealed  by  the  volt- 
meter test,  it  will  be  unnecessary  to  open  the  coil, 
as  the  resistance  drop  with  the  coil  under  known 
compression  shows  its  condition. 

ARMATURE  CLEARANCE 

167.  Introductory    Remarks.      Except    for    an 
armature    occasionally    "getting    away    from    the 
inspector"  or  a  bearing  giving  trouble  that  could 
not  be  foreseen,  there  is  no  excuse  for  armatures 
rubbing  the  pole-pieces.    With  good  lubrication  fg 
in.    of  babbitt  will   last  at  least  two  months: — 
armatures  do  not  go  down  on  the  pole-pieces  in 
unguarded  moments,  but  rather  as  the  result  of 
unguarded  weeks. 


ELECTRIC  CAR  EQUIPMENT  67 

168.  Preliminary  Symptoms.     One  of  the  first 
symptoms  of  low  bearings  is  difficulty  in  keeping 
lubricant  in  the  grease  boxes.    Even  slight  rubbing 
acts  like  a  brake  on  the  core,  heating  the  motor 
mechanically  by  friction  and  electrically,  because 
of  the  greater  current  required  to  overcome  the 
friction  of  the  rubbing  core;  the  increased  tempera- 
ture of  the  motor  thins  the  lubricant  and  it  runs 
through,   precipitating   a   hot  box.      This  heated 
condition  is  sometimes  called  "a  hot  motor." 

169.  As  the  core  lowers  still  more,  the  friction 
increases   and   the   car   breakers   begin    to   blow, 
the  friction  finally  becoming  sufficiently  great  to 
lock  the  armature  or  to  burn  it  out. 

170.  Inspection  by  Light.  Most  clearance  inspec- 
tions are  made  at  night, — not  the  best  time  in  the 
world  for  any  inspection.     Modern  motors  have 
front  and  rear  hand-holes  in  line  with  the  lower  air- 
gap  of  the  motor.  If  the  eye  be  applied  to  the  front 
hole  while  a  light  is  held  opposite  the  back  hole, 
the  clearance  can  be  judged,  although  an  inex- 
perienced man  may  be   confused  by   a  peculiar 
perspective  effect  due  to  shadows. 

171.  Inspection  by  Gage.    Gage  inspection  con- 
sists in  shoving  strip  fiber  between  the  poles  and 

!•*-,/' 


V* 


FIG.  56  FIG.  57 

core  to  test  the  clearance.     The  gage  may  be  a 
single  piece  of  minimum  thickness,  as  in  Fig.  56, 


68  MISCELLANEOUS  TESTS  OF 

or  it  may  be  several  pieces  one  of  which  is  of 
minimum  thickness,  as  in  Fig.  57.  The  first  type 
is  the  simplest,  but  the  second  has  the  advantage 
that  an  approximate  idea  of  the  thinness  of  the 
gap  is  given,  even  when  the  gap  is  not  too  thin. 
In  either  case,  if  the  minimum  thickness  jams 
when  shoved  between  the  pole  and  core,  the  car 
should  be  "held  in." 

172.  Note.     A  marked  wedge-shaped  gage  has 
been  suggested,  to  be  applied  at  the  front  end  of 
the  air-gap.     As  the  front  clearance  may  be  good, 
while  the  back  clearance,   where  greater  bearing 
wear  obtains,  may  be  bad,  the  straight  gage  that 
is  shoved  through  to  the  rear  end  is  to  be  preferred. 

173.  Inspection  by  Schedule.     This  means  the 
appointing  of  certain  days  on  which  certain  cars 
are  to  be  inspected.    The  method  has  the  advantage 
that  the  car  is  held  for  a  specified  object  and  under 
this  condition  the  object  is  likely  to  be  accom- 
plished.     Where    lubrication    is    systematic    and 
effective,  the  method  is  a  good  one,  otherwise  not. 

174.  Conclusion.     Armature  rubbing  is  gener- 
ally attributed  to  the  lower  pole-pieces,  but  this 
is  not  always  the  case.    Worn  housings  or  eccentric 
bearings  may  permit  the  core  to  be  drawn  against 
the    top    pole-pieces.      Loose    top    pole-pieces    or 
projecting  laminations  or  beads,   due   to   former 
short-circuits,  may  be  responsible  for  rubbing  in 
the  upper  air-gap. 

175.  Considerable    space    has    been    given    to 
armature  clearance,  but  too  much  could  not  well 


ELECTRIC  CAR  EQUIPMENT  69 

be  given.  Inasmuch  as  increased  air-gap  thickness 
decreases  the  effect  of  armature  reaction,  thereby 
decreasing  sparking,  and  greatly  reduces  the  most 
expensive  of  operating  troubles — rubbing,  it  would 
seem  that  designers  might  well  make  sacrifices  in 
other  respects  and  put  out  motors  with  air-gaps 
sufficiently  thick  to  survive  the  average  system 
of  armature  clearance  neglect. 


PART  II— MOTION    TESTS 


MOTOR  BALANCE  TESTS 
VOLTMETER  METHOD 

176.  Introductory  Remarks.  Balance  tests  are 
made  to  see  that  the  motors  on  a  given  car  are 
electrically  and  magnetically  balanced,  so  that 
they  will  divide  the  load  equally.  If  two  motors 
are  balanced,  voltage  applied  to  them  connected 
in  series,  will  divide  equally  between  them,  because 
as  their  counter  e.m.f.s  and  ohmic  resistances  are 
equal,  so  are  their  effective  resistances;  and  as 
voltage  distribution  in  a  series  circuit  is  the  same 
as  that  of  the  resistance,  the  drop  across  one  motor 
will  equal  that  across  the  other.  Also,  with  the 
motors  in  parallel,  the  current  will  divide  equally 
between  them,  because  the  effective  resistance  of 
each  of  the  independent  motor  paths  is  the  same. 
Great  difference  in  the  distribution  of  voltage  or 
division  of  current  may  be  due  to  any  of  the 
following  conditions : — 

1.  Open  motor  frame. 

2.  Baked,    short-circuited,   wrongly   connected 

or  grounded  field  coils  or  coils  with  the 
wrong  number  of  turns; — all  of  these 
irregularities  weaken  the  field  magnetism, 
decrease  the  counter  e.m.f.  and  lessen  its 
ability  to  regulate  the  current. 
?n 


ELECTRIC  CAR  EQUIPMENT 


71 


3.  Dissimilar  armatures  (one  a  three-turn  and 

the  other  a  four- turn,  for  example)  will 
unbalance  the  counter  e.m.f.s  and  cause 
unequal  sharing  of  load. 

4.  A  difference  in  the  sizes  of  the  pinions,  gears 

or  wheels  will,  by  affecting  the  armature 
speeds,  unbalance  the  counter  e.m.f.s. 

5.  Wrongly  set  brushes,  by  changing  the  effect 

of  armature  reaction,  unbalance  the  mo- 
tors. The  existence  of  several  of  these 
conditions,  to  a  small  degree  in  each  case, 
will  materially  affect  the  balance  and  it 
may  be  hard  to  locate  the  most  responsible 
cause. 

177.  Two-motor  Car.  Fig.  58  is  a  sketch  of  the 
current  path  on  a  two-motor  car  with  the  motors  in 
series.  Voltmeter  V  is  connected  across  No.  1 


Voltmeter 

FIG.  59 

armature  and  V2  across  No.  2.     A  single  voltmeter 
can  be  used  with  a  change-over  switch ,  as  indicated 


72  MISCELLANEOUS  TESTS  OF 

in  Fig.  59,  but  this  has  the  objection  that  simul- 
taneous readings  cannot  be  taken. 

178.  Directions.     To  conduct  a  voltmeter  bal- 
ance test  on  a  two-motor  car,  Run  the  car  onto  a 
level  track  or  uniform  grade,  300  ft.  long.     With 
motors  in  full  series,  when  the  speed  becomes  uni- 
form, as  indicated  by  the  sound  of  the  gears  or 
by  the  steady  needle  of  an   ammeter  placed  in 
circuit  for  that  purpose,  read  both  meters;  assum- 
ing the  meters  to  be  correct,  if  their  readings  are 
equal,  the  motors  are  balanced. 

179.  Note.     If  one  meter  indicates  over  10% 
more  than  the  other,  conditions  must  be  investi- 
gated by  inspection. 

180.  Note.     The  sum  of  the  readings  cannot 
equal  the  voltage  of  the  line,  because  fields,  car- 
wires  and  contacts  have  resistance  through  which 
there  will  be  some  drop.     On  a  number  of  cars 
tested  at  an  average  of  500  volts,  each  motor  aver- 
aged from  235  volts  to  240  volts.     In  one  case  one 
meter  read  200  volts  and  the  other  270  volts — a 
difference  of   35%.      The  motor   with   the  lower 
voltage  was  found  to  have  carbonized  field  coils. 

181.  Note.     To    tell    if   the    difference    in    the 
readings  exceeds  10  per  cent,  the  per  cent,  differ- 
ence can  be  calculated  as  follows: 

182.  Rule.    To  calculate  the  per  cent,  difference 
in  the  readings  of  two  meters,  Divide  the  difference 
in  the  readings  by  the  smaller  reading,  then  mul- 
tiply by  100. 


ELECTRIC  CAR  EQUIPMENT  73 

183.  Example.     In  a  balance  test,  one  meter 
read  200  volts  and  the  other  270  volts.     What  is 
the  per  cent,  difference  in  these  readings? 

184.  Solution.     270-200  =  70;    and  70-*-200  = 

0.35;    and  0.35x100  =  35%. 

185.  Four-motor   Car.     Fig.    60   indicates   the 
current  path  through  the  motors  on  a  four-motor 
car,  with  the  controller  in  full  series.     Here  two 
motors  are  paired  in  parallel  and  the  two  pairs  are  in 
series.    Balance  readings  would  not  be  taken  under 
this  condition,  for  there  would  be  no  direct  way  of 

Arm     F(.eLd  Arm    Field 


s     /  i 

Arm.  FieLd      / 


FIG.  60 

telling  to  which  motor  a  low  reading  might  be  due. 
Accordingly,  one  of  each  parallel  pair  is  cut  out  and 
the  test  made  on  the  remaining  pair  in  series. 

186.  Directions.     To  make  a  voltmeter  balance 
test  on  the  motors  of  a  four-motor  car,  Draw  the 
brushes  on  one  of  each  of  the   parallel  motors; 
then  make  the  test  as  on  a  two-motor  car. 

187.  Note.    Assuming  motors  1  and  2  to  be  on 
one  truck  and  3  and  4  on  the  other,  Draw  the  brushes 


74  MISCELLANEOUS  TESTS  OF 

on  1  and  3  and  test  2  and  4;  then  draw  the  brushes 
on  2  and  4  and  test  1  and  3. 

LAMP  CIRCUIT  METHOD 

188.  Two-motor   Car.     The   lamp    circuit   test 
depends  on  the  same  principles  of  voltage  distribu- 
tion as  the  test  just  described;    lamp  circuits  are 
used  instead  of  meters.     The  number  of  lamps  to 
be  connected  in  series  in  each  test  circuit  depends  on 
the  voltage  of  the  line  and  on  the  rated  voltage  per 
lamp. 

189.  Rule.     To  find  the  number  of  incandescent 
lamps  to  be  used  in  series  on  a  line  of  given  voltage, 
Divide  the  line  voltage  by  the  voltage  rating  of 
the  lamps  to  be  used. 

190.  Example.     How  many  50-volt  lamps  can 
be  safely  used  in  series  across  a  750- volt  line? 

191.  Solution.     750-7-50=15  lamps. 

192.  Note.     Where    the    line    voltage    is    not 
exactly  divisible  by  the  lamp  voltage,  use  the  next 
higher  number  of  lamps. 

193.  Note.     The  lamp   test  will   indicate   dis- 
crepancies due  to  wrongly   connected,   grounded, 
short-circuited  or  badly  roasted  fields,  but  will  not 
indicate  slight  roasting  or  brush  error. 

194.  Assuming  500  volts  on  the  line  and  two 
test  circuits  of  five  100-volt  lamps  each,  a  lamp 
circuit  balance  test  is  as  follows: — 

195.  Directions.     To  make  a  balance  test  with 
lamp  circuits,  Operate  the  car  as  directed  in  Art. 
177  and  with  lamps  connected  as  in  Fig.   61;    if 


ELECTRIC  CAR  EQUIPMENT  75 

the  motors  are  approximately  balanced  all  lamps 
will  glow  alike;  should  one  circuit  glow  brighter, 
interchange  the  test  circuits  to  see  that  the  differ- 
ence is  not  in  the  lamps  themselves;  if  the  same 
motor  now  causes  the  brighter  circuit,  the  dimmer 
circuit  indicates  an  irregular  motor  to  be  investi- 
gated. With  a  field  coil  connected  backward  or 


Arm.     rieiof  Arm     FieLct 


with  roasted  fields,  the  lamps  on  the  good  motor 
will  glow  to  almost  full  brilliancy,  while  those  on 
the  bad  motor  may  not  appear  to  glow  at  all. 
To  make  more  decided  indications,  Unscrew  a 
lamp  in  the  dim  circuit,  drop  a  cent  in  the  socket  and 
replace  the  lamp.  Repeat  this  short-circuiting  of 
the  lamps  until  the  dim  circuit  glows. 

196.  Note.     By  using  50-volt  lamps  and  chang- 
ing the  number  in  the  test  circuits  until  all  glow 
alike,  the  voltage  across  each  motor  can  be  approxi- 
mated by  the  following  rule : — 

197.  Rule.     To  find  the  voltage  per  motor  in 
a  balance  test  from  the  number  of  lamps  lighted  to 
equal  brightness  and  the  total  voltage  across  the 
two  motors  in  series,  Divide  the  total  voltage  across 


76  MISCELLANEOUS  TESTS  OF 

the  motors  by  the  number  of  lamps  to  get  the  volt- 
age per  lamp,  and  multiply  by  the  number  of  lamps 
on  each  motor. 

198.  Example.     In  a  balance  test,   all  lamps 
glow  alike,  one  of  the  motors  lighting  five  and  the 
other,  three.    If  470  volts  act  across  the  two  motors, 
what  is  the  voltage  across  each  motor? 

199.  Solution.     470-4-8  =  59;    5x59-295,  the 
voltage   acting  on  one   motor.      59x3=177,   the 
voltage  across  the  other. 

200.  Note.     If  all  lamps  glow  at  full  brilliancy, 
then,  to  get  the  voltage  per  motor,  Multiply  the 
rated  voltage  of  one  lamp  (marked  on  its  base)  by 
the  number  of  lamps  on  the  motor. 

201.  Four-motor    Car.      The    connections    for 
the  lamp  test  on  a  four-motor  car  are  those  of  Fig. 
60,  except  that  lamps  are  used  instead  of  meters. 
The  test  is  conducted  in  the  same  manner. 

AMMETER  METHOD 

202.  Introductory    Remarks.       Ammeters,     or 
their  equivalent,   can  be  used  to  determine  the 
current  division  between  two  motors  in  parallel. 
Voltmeters  cannot  be  usefully  applied  to  the  mo- 
tors in  parallel,  because  their  voltages  are  then 
necessarily  the  same,  although  their  current  may  be 
different ;  nor  can  an  ammeter  give  useful  informa- 
tion when  the  motors  are  in  series,  the   current 
through  them  then  being  the  same,  although  their 
drops  may  not  be. 

203.  Two-motor  Car.     The  connections  for  an 


ELECTRIC  CAR  EQUIPMENT  77 

ammeter  test  on  a  two-motor  car  are  given  in  Fig. 
62 ;  a  meter  is  cut  in  with  the  field  lead  of  each  motor, 
care  being  taken  to  connect  the  positive  side  of  the 

Arm.    Field 

/2 


FIG.  62 

meter  with  the  positive  side  of  the  circuit.  When 
the  motors  are  in  series,  then  the  meters  are  also  in 
series,  and,  if  correct,  will  indicate  the  same  current. 
On  throwing  the  motors  to  parallel,  however,  each 
motor  will  include  a  meter  that  will  indicate  the 
current  of  only  that  motor;  assuming  the  meters 
to  be  correct,  if  they  then  indicate  equal  currents, 
the  motors  are  balanced;  if  the  difference  in  the 
readings  exceeds  five  per  cent,  of  the  lower  reading, 
however,  the  cause  must  be  located  and  removed. 

204.  Note.     Except    on    cars    equipped    with 
interpole  motors,  the  meters  should  not  be  cut  into 
the  armature  leads,  because  ordinarily  the  car  is 
reversed  by  reversing  the  armature  currents  and 
the  meter  deflections  would  reverse  with  them. 
Also  as  the  armature  wires  are  reversed  in  the  No. 
2  controller,  a  meter  would  deflect  properly  when 
operating  from  one  end  of  the  car  but  not  from  the 
other. 

205.  Note.     An  exception  is  made  of  interpole 
motors,  because  here  the  fields  are  reversed  instead 
of  the  armatures. 


78  MISCELLANEOUS  TESTS  OF 

206.  Four-motor  Car.     Where  four  ammeters 
are  available,  it  is  well  to  cut  a  meter  in  with  each 
motor,   otherwise  the  motors  must  be  tested  in 
pairs;   in  this  case  it  will  not  be  necessary  to  draw 
any  brushes,  because  on  all  parallel  notches  the 
motor  paths  are  independent,  each  meter  indicating 
the  current  of  the  motor  with  which  it  is  in  series. 
To  check  results,  the  motors  can  be  tested  in  several 
combinations  of  pairs: — 1  and  2;   1  and  3;   1  and  4; 
2  and  3;   2  and  4  and  3  and  4. 

MILLI-VOLTMETER  METHOD 

207.  Introductory  Remarks.      Milli-voltmeters. 
or  low  reading  voltmeters  can  be  used  for  making 
a  balance  test.     When  so  used,  the  instruments 
really  constitute  ammeters.     With  a  50  or  75-volt 
voltmeter,  the  motor  field  coils  can  be  used  as  the 
standard  resistances  with  which  to   connect  the 
meters  in  parallel;   but  in  this  case,  the  coils,  the 
drops  on  which  are  being  compared,  must  have 
equal    resistances.      Where    milli-voltmeters    are 
used,  equal  lengths  of  the  same  size  of  copper  wire 
will  do  for  standard  resistances.    The  main  precau- 
tion is  to  see  that  no  meter  is  subjected  to  a  voltage 
exceeding   its  capacity.      (See  Art.    55,  page  70, 
"Shop  Tests  of  Electric  Car  Equipment.") 

208.  Two-motor  Car.     The  connections  for  a 
milli- voltmeter  balance  test  on  a  two-motor  car; 
are  given  in  Fig.  63.     Cut  into  the  field  jumper  of 
each  motor  (see  Notes  205  and  206),  is  a  piece  of 
copper  wire  sufficiently  large  to  carry  the  current 


ELECTRIC  CAR  EQUIPMENT  79 

without  heating  and  of  such  resistance  that  maxi- 
mum current  will  not  produce  a  drop  exceeding  the 
range  of  the  meter  to  which  it  is  connected  as  indi- 
cated. Either  the  current  values  of  corresponding 
deflections  must  be  ascertained,  or  the  values  of 
resistances  r  and  rr  must  be  different  and  such  that 
equal  deflections  on  the  meters  have  the  same  cur- 

Arm.   Field 
1 


FIG.  63 

rent  value.  With  similar  instruments  or  with  their 
deflections  adjusted  to  have  equal  values,  the 
deflections  are  simply  compared  when  the  car 
operates  at  uniform  speed  with  the  motors  in  full 
parallel.  If  the  difference  in  their  deflections 
exceeds  five  per  cent,  of  the  lower  deflection,  the 
conditions  must  be  investigated. 

209.  Four-motor  Car.    The  test  on  a  four-motor 
car  is  the  same  as  the  preceding,  except  that  the 
meters  and  their  shunts  are  to  be  applied  to  two 
motors  at  a  time. 

210.  Current    Values    of    Deflections    may    be 
required.     As  a  deflection  is  due  to  a  drop  caused 
by  motor  current,  each  deflection  corresponds  to  a 
certain  current  in  the  motor  with  which  the  meter 
is  used.     The  determination  of  the  values  of  meter 
deflections  is  called  calibrating  the  meter. 

211.  Directions.     To  calibrate  dissimilar  milli- 


80  MISCELLANEOUS  TESTS  OF 

voltmeters  so  that  the  readings  on  one  can  be  under  • 
stood  in  terms  of  the  other,  Connect  a  variable 
resistance,  R,  Fig.  64,  an  ammeter,  and  the  two 
milli- voltmeters  with  their  shunts  properly  paired, 
in  series.  Adjust  the  current  until  the  lower  read- 
ing milli- voltmeter  deflects  a  maximum,  noting 
the  readings  of  the  higher  reading  milli-voltmeter 
and  ammeter.  Calling  the  ammeter  A,  the  higher 
reading  milli-voltmeter  B  and  the  lower  reading 


r 

Ammeter 


milli-voltmeter  C,  when  A  deflects  60,  suppose  B 
to  deflect  60  and  C  100  divisions;  then  1  division 
on  B  means  1  ampere  and  1  division  on  C,  f  ampere. 
In  using  the  meters,  B  can,  then,  be  read  directly, 
but  the  deflections  of  C  must  be  multiplied  by  f 
to  get  their  values  in  amperes. 

212.  Note.    The  readings  are  taken  during  the 
test  and  necessary  reductions  made  afterward. 

213.  Adjusting  Meters  to  Read  the  Same,  con- 
sists in  changing  the  resistance  of  r  or  r',  Fig.  64, 
until  given  current  produces  the  same  deflection  on 
both  milli- voltmeters. 

214.  Directions.      To    adjust    two    milli-volt- 
meters  to  read  the  same  for  given  current,  Vary 
the  length,  hence  resistance,  of  either  shunt,  until 
both  milli-voltmeters  deflect  the  same. 


ELECTRIC  CAR  EQUIPMENT  81 

215.  Note.  It  is  advisable  to  so  adjust  the  shunts 
that  the  whole  scale  of  the  lower  reading  instru- 
ment may  be  available  because  they  will  then  be 
read  more  accurately. 

216.  Adjusting  Meters  to  Read  Direct,  a  refine- 
ment   of    the    preceding    adjustment,    consists    in 
varying  r  and  r',  until  each  of  the  milli- voltmeters 
deflects  one  division  per  ampere  on  A. 

217.  Directions.       To    adjust    two    milli-volt- 
meters  to  read  direct,  with  the  connections  of  Fig. 
64,  Repeatedly  open  the  circuit,  change  the  length 
of  r  or  r',  close  the  circuit,  note  the  deflections  of 
all  meters  and  get  the  values  of  r  and  r'  such  that 
with  a  current  of  50  amperes  on  the  ammeter  both 
of  the  milli- voltmeters  deflect  50  divisions  on  their 
scales. 

218.  Note.    Milli- voltmeters  can  be  bought  with 
shunts    for    direct    current    readings.       A    meter 
adjusted  to  read  direct  with  one  shunt  will  not, 
however,  read  direct  with  another  shunt. 

219.  Use  of  a  Change-over  Switch,  except  in 
extreme  cases,  is  to  be  avoided;    where  but  one 


FIG.  65 

ammeter  or  milli- voltmeter  is  available,  however, 
a  double-pole,  double-slide  switch,  K,  Fig.  65,  can 


82  MISCELLANEOUS  TESTS  OF 

be  made  to  throw  the  meter  from  one  motor  circuit 
to  the  other  without  breaking  the  circuit  of  either. 
The  ammeter  or  the  milli-voltmeter  and  its  shunt 
are  connected  across  the  centers  of  the  switch, 
the  end  connecting  posts  being  cut  into  the  respec- 
tive motor  circuits.  With  the  slide  in  the  position 
shown,  the  meter  is  cut  in  with  the  No.  1  or  upper 
motor;  by  throwing  the  slide  down,  the  instru- 
ment is  transferred  to  the  other  motor  circuit. 

VALUE  AS  A  FIELD  TEST 

220.  The  voltmeter  balance  test  is  well  adapted 
to  finding  baked  field  coils.  Where  the  coils  in 
both  motors  have  weakened  at  about  the  same  rate, 
the  value  of  the  test,  as  ordinarily  made,  is  a  mini- 
mum; but  uniform  deterioration  of  all  the  coils 
of  a  car,  while  possible,  is  a  rare  exception.  The 
possibility  of  this  condition  is  but  the  greater  reason 
for  occasionally  giving  motors  new  sets  of  coils  to 
be  tested  against  fields  that  long  sendee  may  have 
deteriorated.  Such  a  test  could  well  be  made  by 
installing  a  newly  equipped  motor  on  a  truck  to 
be  towed  by  any  car  having  suspected  fields. 
During  a  test,  the  towed  motor  would  be  connected 
in  series  with  the  car  motor  circuit,  the  drops  on 
all  three  armatures  being  simultaneously  taken  at 
uniform  car  speed.  In  such  a  test,  the  voltmeter 
would  reveal  weak  fields  before  they  had  commenced 
to  cause  vicious  sparking,  blowing  of  fuses  and 
breakers,  or  to  knock  out  armatures. 


MOTOR  HEATING  TESTS 
OBJECTS  OF  HEAT  TESTS 

221.  Object    of    Factory   Test.      Factory   heat 
tests  are  made  to  determine  the  temperature  rise 
when  a  motor  is  run  at  full  load  a  given  time — 
usually  0.5  hour  in  each  direction.     A  full  heat  test 
is  seldom  run  in  a  repair  shop,  except  for  some 
special  purpose — usually  to  test  the  effect  of  pro- 
posed changes. 

222.  Object  of  Shop  Test.     In  car  shops,  heat 
tests  may  be  made  on  repair  armatures  or  to  deter- 
mine the  effect  of  milling  core  slots  or  modifying 
the  winding.     Car-house  men  know  that  a  motor 
with  baked  fields  gets  hot  enough  to  give  bearing 
troubles  due  to  the  lubricant  thinning.     In  service, 
the  field  automatically  regulates  the  motor  current, 
so  that  if  carbonization  weakens  the  field,  the  motor 
takes  excessive  current  and  heats.     In  a  shop  test, 
however,  the  current  is  held  at  a  predecided  value 
and  the  only  evidences  of  weak  field  would  be 
increased   speed   and   sparking.      With   the   same 
current,  a  baked  field  heats  less  than  a  good  one 
because  its  resistance  is  less  and,  therefore,  cannot 
absorb  as  much  energy.    In  a  heat  test,  two  motors 
are  geared  to  an  axle  carried  in  suitable  bearings. 
The  frames  remain  in  place  and  are  adapted  for 
readily   installing   and   removing   armatures   that 
are  to  be  tested. 


84 


MISCELLANEOUS  TESTS  OF 


223.  Note.     The  rate  at  which  heat  energy  is 
produced  in  a  field  is  equal  to  the  current  multi- 
plied by  the  drop  across  it.     If  the  resistance  of 
the  field  is  less,  the  drop  for  given  current  will  also 
be  less;  therefore,  drop  multiplied  by  current  will 
be  less  and  the  field  will  not  heat  as  much. 

TEST  CONNECTIONS 

224.  Self  Excited  Method.     A  dynamo  is  said 
to  be  self  excited  when  it  supplies  its  own  field 
current.     Fig.  66  gives  connections  for  all  circuit 
combinations  required  in  a  heat  test  in  which  both 


machines  in  turn  are  run  as  motor  and  dynamo 
and  in  both  directions.  The  field  and  armature 
wires  are  run  to  a  controller  that  has  the  usual 
trolley  and  ground  wires  and  resistance.  Each 
machine  has  a  separate  reverse  switch,  for  with 
given  connections  a  self  excited  dynamo  will 
generate  in  but  one  direction ;  as  the  dynamo  must 
load  the  motor  in  both  directions,  extra  switches 
save  connecting  and  disconnecting.  At  a  and  b 
are  single-throw,  single-pole  switches  not  required 


ELECTRIC  CAR  EQUIPMENT 


85 


to  open  an  active  circuit.  When  using  machine 
No.  1  as  motor,  switches  a  are  open  and  b  closed; 
with  No.  2  as  motor,  switches  b  are  open  and  a 
closed.  In  Fig.  66,  a  and  b  are  set  for  running  No. 
2  as  motor  and  No.  1  as  dynamo.  The  dynamo 
is  always  cut  out  in  the  controller.  In  series  with 
the  trolley,  but  not  shown,  is  an  ammeter  for 
keeping  the  current  constant.  At  c  are  two  small 
hooks;  a  piece  of  small  fuse  wire  laid  across  c 
short-circuits  the  water  rheostat  and  enables  the 
dynamo  to  generate  promptly  should  the  water 
give  trouble. 

225.  Separately  Excited  Method.  A  dynamo  is 
said  to  be  separately  excited  when  its  field  is  mag- 
netized by  current  due  to  an  independent  source; 
in  the  present  case,  the  dynamo  field  is  magnetized 


by  current  from  the  motor  circuit.  A  dynamo  so 
excited  will  generate  in  either  direction.  The 
separate  excitation  method  is  ill  adapted  where 
temperature  measurements  are  to  be  taken,  because 
the  drop  in  the  dynamo  field  reduces  the  voltage 
applied  to  the.  motor,  thereby  decreasing  its  arma- 


86  MISCELLANEOUS  TESTS  OF 

ture  speed  and  certain  losses  depending  on  it. 
The  requirements  and  connections  are  the  same  as 
those  of  the  preceding  test,  except  that  the  extra 
reverse  switches  are  omitted,  and  are  shown  in  Fig. 
67.  When  machine  No.  1  is  used  as  motor,  double- 
throw,  double-pole  switch  K  and  single-throw, 
single-pole  switch  b  are  in  the  positions  shown, 
switch  a  being  in  its  dotted  position  or  open.  When 
No.  2  is  the  motor,  K  and  a  are  closed  and  b  opened. 
The  fields  of  the  two  machines  are  connected  in 
series  as  indicated. 

TEST  INSTRUCTIONS 

226.  Self  Excited  Method.  Having  installed 
two  armatures,  insert  brushes  and  sandpaper  them 
to  fit  the  commutator.  Put  a  handful  of  salt  in 
the  water  box,  shove  the  plates  close  together, 
see  that  no  one  is  in  a  position  to  get  hurt,  then 
start  the  test;  if  the  dynamo  fails  to  generate, 
reverse  its  field;  if  it  still  fails  to  "pick  up,"  lay  a 
small  wire  across  hooks  c ;  with  correct  connections 
and  no  open-circuit,  the  machine  will  now  generate, 
blowing  the  fuse  at  c.  The  strong  residual  magnet- 
ism due  to  the  short-circuit  current  will  enable  the 
dynamo  to  generate  through  the  water  box.  Having 
run  at  full  load  for  half  an  hour,  the  test  is  shut 
down,  the  controller  reverse  switch  thrown,  the 
dynamo  field  reversed,  the  test  started  and  run 
for  another  half  hour  at  full  load.  If  both  arma- 
tures are  to  be  tested,  the  test  is  again  shut  down, 
machine  No.  2  cut  out  at  the  controller,  No.  1  cut 


ELECTRIC  CAR  EQUIPMENT  87 

in,  switches  a  opened  and  b  closed  and  the  same 
tests  run  as  in  the  first  case. 

227.  Note.      A  single  ground  will  not  interfere 
with  the  operation  of  a  circuit,  but  a  second  ground 
forms  a  by-path  through  which  there  can  be  a 
short-circuit  current.     Accordingly,  in  the  preced- 
ing test,  either  the  test  rack  must  be  grounded, 
or  a  point  in  the  copper  part  of  the  motor  circuit 
connected  to  the  motor  frame  with  a  small  fuse 
wire,  which  will  blow,  should  a  ground  develop  on 
the  motor  during  the  test. 

228.  Separately  Excited  Method.     This  test  is 
run  the  same  as  the  preceding  except  that  there  are 
no  reverse  switches. 

TEST  READINGS 

229.  Shop  Test.     In  this  test  the  current  is 
kept  at  full  load  and  the  shaft  speed  taken  at  the 
beginning  and  end  of  test.     When  taking  speed, 
the  current  should  be  right  and  the  voltage  as  near 
right  as  practicable.    The  initial  speed  will  exceed 
the  final  speed,  owing  to  the  greater  drop  in  the 
heated  windings.     If  the  speed  is  stated  at  500 
volts  and  the  voltage  available  is,  say,  but  450, 
the  speed  at  500  volts  must  be  calculated :  this  can 
be  done  by  the  following  rule : — 

230.  Rule.    To  calculate  the  speed  at  500  volts 
from  that  at  test  voltage,   Divide   the   standard 
voltage  by  the  test  voltage  and  multiply  by  the 
test  speed. 

231.  Example.     The  speed  of  a  shaft  was  170 


88  MISCELLANEOUS  TESTS  OF 

revolutions  per  minute  at  450  volts.  What  would 
have  been  the  speed  in  revolutions  per  minute  at 
500  volts? 

232.  Solution.     500^450=1.11  and  170xl.ll 
=  188  revolutions  per  minute. 

233.  Note.     During   the   test   the   machine   is 
watched  for  hot  bearings,  sparking,  bent  armature 
shaft,  loose  or  eccentric  commutator,  open-circuit, 
short-circuit,  endplay  and  grounds. 

234.  Temperature  Test.     If  temperature  rise  is 
to   be   measured,    voltage   and   current   must   be 
maintained  at  standard  values.     The  temperature 
of   the   atmosphere   is   noted   and    the    armature 
resistance  measured.     Noting  the  time,  the  test  is 
started,  full  load  put  on  and  maintained  constant 
for  one  hour.    The  test  is  then  shut  down,  a  ther- 
mometer placed  on  the  armature  and  covered  with 
waste.     In  the  meanwhile  the  armature  resistance 
is  again  measured.     After  about  25  minutes  the 
thermometer  is  read. 

235.  Temperature    Rise,    calculated    from    the 
rise  in  resistance,  is  added  to  the  room  temperature 
at  the  time  of  starting,  to  get  the  final  temperature 
of  the  armature. 

236.  Rule.     To  calculate  the  temperature  rise 
of  a  copper  winding  from  its  rise   in  resistance, 
Subtract  the  resistance  cold  from  the  resistance 
hot,  divide  by  the  resistance  cold  and  multiply 
by  258.    The  temperature  rise  added  to  the  initial 
temperature,  gives  the  final  temperature  in  degrees 
centigrade. 


ELECTRIC  CAR  EQUIPMENT  89 

237.  Example.     With  a  room  temperature  of 
25  degrees  centigrade  (25°  C.),  the  cold  resistance 
of  a  motor  field  winding  is  0.2  ohm  and  at  the  end 
of  one  hour's  run  at  full  load,  the  field  resistance 
measures  0.26  ohm.      Wanted  (a)  temperature  rise 
and  (6)  final  temperature  of  the  winding. 

238.  Solution,  (a)  0.26-0.20  =  0.06;    and  0.06 
-0.20  =  0.3;   and  (6)  0.3x258  =  77.4°C.,  tempera- 
ture rise,  Ans.  77.4+25=102.4°C.,  Ans. 

239.  Note.     The  calculated  final  temperature 
will  exceed  that  read  on  the  thermometer,  because 
the  resistance  method  reaches  the  hottest  part  of 
the  winding,  while  the  thermometer  does  not. 

240.  Comparison  of  Thermometers  can  be  effec- 
ted as  follows: — 

241.  Rule.     To  convert  degrees  centigrade  into 
degrees  fahrenheit,  Multiply  the  °C.  by  9,  divide  by 
5  and  add  32. 

242.  Example.     In  Ex.    12,  express  the  final 
temperature  as  °F. 

243.  Solution.     9x102.4  =  921.6;    and  921.6-=- 
5  =  184.32;   184.32  + 32  =  216.32°F. 

244.  Rule.     To  convert  degrees  fahrenheit  into 
degrees  centigrade,  Subtract  32  from  °F.,  multiply 
by  5  and  divide  by  9. 

245.  Example.     Express  216.32°F.  as  °C. 

246.  Solution.     216.32-32  =  184.32;  and  184.- 
32X5  =  921.6;  and  921.6-i-9=102.40C. 


EFFICIENCY  TESTS 
DEFINITIONS 

247.  Efficiency.    The  efficiency  of  a  machine  is 
the  ratio  of  the  power  given  out  to  the  power  put 
into  it,  both  quantities  being  measured  at  the  same 
time.     The  output  is  the  numerator  of  a  fraction 
of  which  the  denominator  is  the  input,  both  being 
expressed  in  the  same  units.    The  fraction  is  always 
less  than  1,  because  no  machine  can  put  out  all 
the  work  put  into  it: — hence  the  failure  of  all 
attempts  at  perpetual  motion. 

248.  Commercial   Efficiency   of   Motors.      The 
commercial  efficiency  of  a  motor  is  the  mechanical 
power   available   at   the   pinion,   divided   by   the 
electrical  power  put  into  the  motor.    It  is  generally 
stated  as  the  mechanical  output  divided  by  the 
electrical  input,  both  being  expressed  in  the  same 
units. 

249.  Electrical  Efficiency  of  Motors.    The  elec- 
tric efficiency  of  a  motor  is  a  fraction,  the  numerator 
of  which  is  the  difference  between  the  electrical 
input  and  electrical  losses  and  the  denominator  of 
which  is  the  electrical  input.     It  is  calculated. 

250.  Expression  of  Per  Cent.  Efficiency.    Know- 
ing the  input  and  output  of  a  machine,  both  ex- 
pressed in  the  same  unit,  the  percentage  efficiency 
can  be  calculated  by  the  following  rule : — 

90 


ELECTRIC  CAR  EQUIPMENT  91 

261.  Rule.  To  get  the  percentage  efficiency 
of  a  machine  from  its  output  and  input,  Divide 
output  by  input  and  multiply  by  100. 

252.  Example.     The  electrical  input  of  a  motor 
is  32,000  watts  and  its  mechanical  output  25,636 
watts.    Wanted  its  percentage  efficiency. 

253.  Solution.     25,636-5-32,000  =  0.8;    and  0.8 
X 100  =  80  percent. 

ELECTRICAL  EFFICIENCY  TEST 

254.  Preliminaries.    As  the  internal  resistance, 
i.e.,  the  combined  field  and  armature  resistances, 
of  a  hot  motor  exceeds  that  of  a  cold  one,  the  hot 
losses  will  exceed  the  cold  losses.    As  the  efficiency 
sought  is  the  efficiency  under  working'  conditions, 
a  machine  must  run  one  hour  at  full  load  before 
measuring  the  resistances  to  be  used  in  the  efficiency 
calculations. 

255.  Calculations.     Knowing  the  test  current, 
voltage  and  internal  resistance  hot,  the  electric 
efficiency  can  be  calculated  as  follows: — 

256.  Rule.     To  get  the  electric  efficiency  of  a 
motor  at  stated  current  and  voltage,  the  internal 
resistance  hot  being  known,  Multiply  voltage  and 
current  to  get  watts  input ;  next,  multiply  internal 
resistance  and  square  of  current  to  get  watt  losses. 
Finally,  divide  the  difference  between  the  input 
and  loss  by  the  input  and  multiply  by  100.     The 
result  is  per  cent,  electrical  efficiency. 

257.  Example.     The  internal  resistance  hot  of 
a  30  hp.   railway  motor  is  0.3  ohm.     Wanted, 


92  MISCELLANEOUS  TESTS  OF 

electrical    efficiency    at    full    load    on    a    500-volt 
circuit. 

258.  Solution.      30     hp.  =  30  X  746     watts  = 
22,380     watts  =  input.   22,380  watts  +  500  volts  = 
44.5    amperes  =  full    current    load;     44.5x44.5  = 
1,980.25  =  square    of    current;     1,980  X  0.3  =  594 
watts  =  losses;    22,380-594  =  21,786  =  difference; 
21 ,786 -=-22,380  =  0.973  =  electrical  efficiency;  0.973 
X  100  =  97. 3  =  per  cent,  electrical  efficiency. 

COMMERCIAL  EFFICIENCY  TEST 

259.  Preliminary.    To  get  commercial  efficiency, 
the  input  must  be  measured  electrically  and  the 
output  mechanically.     The  electrical  input  can  be 
measured  with  voltmeter  and  ammeter ;  the  output 
is  measured  with  a  brake.     As  in  the  preceding 
case,    the  motor  must   be   heated   before   taking 
measurements. 

260.  Mechanical  Output.    Fig.  68  shows  a  form 
of  brake  used  to  measure  the  output  of  a  motor. 
M  is  an  iron  pulley;   it  is  flanged  on  the  outside  to 
guide  a  steel  strap,  one  end  of  which  fastens  to 
the  lower  end  of  clamp  E  and  the  other  end  to  the 
upper  end  of  E  and  also  supporting  a  variable 
weight,  W,  on  hanger  D;  M  is  flanged  on  the  inside 
to  hold  water  poured  in  after  starting  the  test,  to 
keep  the  pulley  cool.    The  grip  of  the  strap  can  be 
varied  with  the  cord  t.    The  armature  turns  from 
left  to  right  and  tends  to  drag  W  around  but  W 
resists  this  tendency.    W  and  E  are  so  adjusted  that 
when  the  motor  takes  the  current  at  which  the 


ELECTRIC  CAR  EQUIPMENT  93 

efficiency  is  to  be  tested,  the  hanger  part  of  the 
strap  is  tangent  to  the  pulley  at  radius  O-T.  The 
motor  is  bolted  down  and  a  guard  may  be  put  over 
the  weights  to  prevent  their  giving  trouble  should 
the  tester  become  confused.  At  full  load  current 


FIG.  68 

and  voltage,  the  armature  speed  is  taken  with  an 
indicator.  Knowing  this  speed  in  revolutions  per 
minute,  the  radius  of  the  pulley  and  weight  W  that 
balances  the  load,  the  output  is  calculated  as 
follows : — 

261.  Rule.     To  get  the  watts  absorbed  by  a 
brake  on  which  weight  W  acts  at  the  circumference 
perpendicular  to  the  horizontal  diameter,  Multiply 
together  the  circumference  of  the  pulley  in  feet, 
the  revolutions  per  second,  the  weight  of  W  in 
pounds  and  1.36. 

262.  Example.     A  loaded  armature  makes  600 
revolutions  per  minute,  sustaining  a  weight  W  =  200 
Ib.  at  a  radius  of  18  in.    Wanted,  watts  output. 

263.  Solution.    3X3. 1416  =  9.4248  ft.  =  circum- 
ference  of   pulley ;     600  -r-  60  =  10  revolutions   per 
second;  1.36X9.4248X10X200  =  25,636  watts  out- 
put. * 


94  MISCELLANEOUS  TESTS  OF 

264.  Note.     The  object  of  multiplying  by  1.36 
is  to  reduce  ft.-lb.  per  second  to  watts,  there  being 
1.36  ft.-lb.  per  second  to  a  watt. 

265.  Electrical  Input.     To  measure  the   elec- 
trical input,  connect  an  ammeter  in  series  with  the 
motor  and  a  voltmeter  across  its  terminals;    the 
watts  input  is  then  calculated  as  follows: — 

266.  Rule.     To  get  the  watts  input  of  a  motor 
from  its  voltage  and  current,  Multiply  the  voltage 
by  the  current. 

267.  Example.     In  the  motor  efficiency  test  of 
Ex.  No.  263,  the  current  is  64  amp.  and  the  voltage 
500  volts.    Wanted,  the  motor  input. 

268.  Solution.     500  volts  X  64  amperes  =  32 ,000 
watts. 

269.  Final   Calculations.      As   the    commercial 
efficiency    is    the    mechanical     output  -5-  electrical 
input,  the  commercial  efficiency  is,  in  this  case, 

25,636-^-32,000  =  0.80;  and  0.80X100  =  80  per 
cent.    Ans. 


ENERGY  ABSORPTION  TESTS 
INTRODUCTORY 

270.  Energy  absorption  tests  are  made  to 
determine  directly  the  average  power  required  to 
operate  a  car  in  service  and  indirectly  other  infor- 
mation used  in  comparing  car  performances. 


Where  cars  are  equipped  with  heat,  light  and 
compressor  circuits,  they  must  be  opened  if  only 
the  energy  absorption  of  the  motors  is  to  be 
determined.  The  record  must  start  and  end  with 
the  trip  and  unusual  delays  must  be  noted. 

WATT-HOUR  METER  METHOD 

271.  The  easiest  way  to  record  an  energy 
absorption  test  is  with  a  watt-hour  meter: — the 
meter  field  is  connected  in  series  with  the  motor 
circuit  and  the  armature,  across  the  line,  as  indicated 
in  Fig.  70.  The  only  readings  to  be  taken  are  at 
the  start  and  finish,  except  that  allowance  must  be 
made  for  unusual  delays.  The  difference  between 
the  start  and  finish  readings,  when  multiplied  by 
95 


96  MISCELLANEOUS  TESTS  OF 

the  constant  of  the  meter,  gives  the  energy  absorbed 
during  the  trip,  expressed  in  watt-hours. 


Wait-hour  meter- 


FIG.  70 

272.  Note.     The  constant,  by  which  all  readings 
are  to  be  multiplied,  is  conspicuously  displayed  on 
the  instrument. 

273.  Note.     Unless  the  instrument  is  flexibly 
mounted  for  railway  work,  it  should  be  spring- 
supported  in  the  car. 

INDICATING  WATTMETER  METHOD 

274.  The    indicating    wattmeter,    a    sketch    of 
the   connections  of  which  is   shown   in   Fig.    71, 
indicates  the  rate  at  which  energy  is  being  absorbed 
by  the  circuit  at  the  instant  of  taking  the  reading. 
The  large  bare  terminals  connect  in  series  with  the 

Wattmeter 

-Fie  Lets  -^ 


FlG.  71 

motor  circuit  and  the  smaller,  rubber  covered 
terminals  across  the  line.  On  pressing  the  button, 
the  dead  beat  needle  indicates  the  existing  rate  of 
energy  absorption  in  the  motor  circuit.  To  get  the 


ELECTRIC  CAR  EQUIPMENT  97 

watt-hours  of  energy  absorbed  in  a  given  time, 
numerous  equi-spaced  readings  taken  during  that 
time  must  be  averaged  and  the  average  multiplied 
by  the  time  in  hours.  The  readings  are  started  and 
ended  with  the  trip  and  the  closer  together  they 
are,  the  more  correct  the  results.  A  satisfactory 
way  to  get  numerous  equi-spaced  readings  is  to 
take  them  deliberately,  and,  as  soon  as  one  is  taken, 
take  another  in  the  same  manner. 

275.  Rule.     To  get  the  watt-hours  absorbed  in 
a  given  time  from  the  readings  of  an  indicating 
wattmeter,  Add  the  readings  and  divide  by  their 
number  to  get  the  average  reading  expressed  in 
watts;   then  multiply  by  the  time  in  hours. 

276.  Example.     In  130  seconds,  the  following 
indicating  wattmeter  readings  were  taken.  Wanted, 
the  watt-hours  absorbed. 

277.  Solution.    80,080+0+0  +  63,750  +  120,750 
+ 0  +  85 ,800  +  27 ,000  +  85 ,000  +  82 ,500  +  0  +  96 ,800 
+  0+0  +0  +  112,000  +  86,350  +0  +  37,800  +0  + 
86,840+81,120+86,350  +  84,530  +  86,940  +  84,530 
=  1,388, 140  =  sum  of  the  readings;    1,388, 140-*- 26 
=  53,390  =  average  watts ;  and  53,390  X  .036  =  1 ,922 
-.04  watt-hours  absorbed  during  the  test. 

278.  Note.     130  seconds  is  2  min.  and  10  sec.  or 
2£  minutes;    the  time  in  hours  is,  then,  2^-^60  = 
0.036  hour. 

VOLTMETER-AMMETER  METHOD 

279.  In  this  test  the  ammeter  is  connected  in 
series  with  the  motor  circuit  and  the  voltmeter 


98  MISCELLANEOUS  TESTS  OF 

across  the  line.  Simultaneous  readings  are  taken 
on  both  and  put  down  opposite  each  other,  as 
indicated  in  the  following  sample  test  sheet  .where 
volts  are  in  the  first  column,  amperes  in  the  second, 
and  their  product,  watts,  in  the  third.  As  the  meter 
readings  must  be  taken  simultaneously,  they  are 
best  taken  by  two  operators  one  of  whom  gives  the 
signal.  If,  as  soon  as  one  set  of  readings  is  taken 
and  put  down,  another  is  taken  and  recorded  in 
the  same  manner,  they  will  be  frequent  and  equi- 
spaced — two  desirable  conditions.  Unless  accus- 
tomed to  take  sight  readings,  the  operator  will  be 
tempted  to  wait  until  a  moving  needle  stops, 
before  taking  a  reading;  this  temptation  must  be 
overcome  or  the  results  may  be  in  error.  The  instru- 
ments should  be  supported  in  boxes  filled  with 
waste  and  before  starting,  the  tester  should  be 
certain  that  the  capacity  of  the  ammeter  is  sufficient 
for  all  currents  likely  to  be  measured.  To  look  after 
possible  short-circuits,  the  ammeter  should  be 
provided  with  a  short-circuiting  switch,  with  which 
to  cut  the  meter  out  should  any  warning  of  short- 
circuit  be  given.  As  the  resistance  of  an  ammeter 
is  low,  the  instrument  will  register  some  current 
even  when  the  short-circuiting  switch  is  closed, 
so  care  must  be  had  to  take  no  readings  with  the 
ammeter  short-circuited,  as  the  test  would  then 
have  to  be  repeated.  After  all  readings  have  been 
taken  and  recorded,  each  voltmeter  reading  is  to 
be  multiplied  by  its  corresponding  ammeter 
reading  and  the  product,  watts,  put  opposite  in 


ELECTRIC  CAR  EQUIPMENT  99 

the  column  marked  W.  This  product  is  the  watts 
or  rate  at  which  energy  was  being  absorbed  by  the 
motor  circuit  at  the  instant  of  taking  the  simul- 
taneous voltmeter  and  ammeter  readings  and  repre- 
sents the  reading  that  an  indicating  wattmeter 
would  have  given. 

ABSORPTION  TEST,  RECORD  SHEETS 

280.     Sample  record  sheet  of  an  actual  voltmeter- 
ammeter  test: — 


Volts      Amp.    Watts 

Volts      Amp.     Watts 

450  X     0=          0 
410X     0=          0 
475X110=52,250 
410  X   85—34850 

560  X     0=            0 
575  X     0=            0 
570  X     0=             0 

390X215=83,850 
460  X   85=39,100 
420  X     0=          0 
460  X     0=          0 

570  X  83=  47,310 
535  X   74=  39,590 
575  X     0=            0 
510X213  =  108,630 

281.  From  data  gotten  before  the  test  and  from 
the  test  readings,  the  following  information 
becomes  available: — 

Car  number 1,526 

Car  weight  (Ibs.) 42,380 

Number  motors  per  car 4 

Rated  hp.  per  motor 40 

Rated  hp.  of  equipment 160 

Full  load  current  (amp.) 239 

Type  of  controller K-6 

Condition  of  rail Good 

Time  of  start  (p.m.) 2.3 

Time  of  stop  (p.m.) 4.4 

Total  duration  (min.) 121 


100  MISCELLANEOUS  TESTS  OF 

Delays  (min.) 18 

Actual  duration  (min.) 103 

Actual  duration  (hr.) . . .' 1 . 72 

Distance  (miles) 17 . 78 

Route Bergen  Turnpike 

Number  voltmeter  readings .  .  509 

Sum  of  voltmeter  readings 262,095 

Average  voltmeter  readings 514 

Maximum  voltmeter  readings 625 

Minimum  voltmeter  readings 360 

Number  ammeter  readings 509 

Number  current  readings 281 

Sum  current  readings 43,773 

Average  current — all  readings 86 

Average  current — current  readings 156 

Maximum  current  readings 355 

Maximum  power  readings  (watts) 191,700 

Number  power  readings 281 

Sum  power  readings 21,851,395 

Average  power — all  readings  (watts) 42,930 

Average  power — current  readings « 77,763 

Average  speed  (miles  per  hr.) 10 . 36 

Total  energy  absorbed  (watt-hours) 73,667.88 

Kilowatts  (Average) 42 .93 

Kilowatt-hours  per  mile 4.14 

Kilowatt-hours  per  ton 3 . 47 

Kilowatt -hours  per  ton-mile 0 . 195 

Kilowatts  per  ton 2.02 

Maximum  hp.  exerted 254 . 20 

Average  hp.  exerted 57 . 50 

Total  energy  absorbed  (horsepower  hours). . .  .  104 

Date  of  test April  10th,  1906 

Chief  observer Edward  Ford 

ANALYSIS  OF  TEST  SHEET 

282.     Weight    of    Car    (Equipped).  The    car 

weight  is  gotten  by  actual  weighing;    if  the  scale 


ELECTRIC  CAR  EQUIPMENT  101 

is  too  small  to  weigh  the  whole  car,  weigh  one  end 
at  a  time  and  add  the  weights. 

283.  Rule.     Given  a  car  weight  in  pounds,  to 
get  its  weight  in  tons,  Divide  the  pounds  weight 
by  2,000. 

284.  Example.    A  car  weighs  42,380  Ib.  Wanted, 
the  weight  in  tons. 

285.  Solution.     42,380-5-2,000  =  21.19  tons. 

286.  Note.     If  the  weight  is  given  in  tons,  and 
the  weight  in  pounds  is  desired,  Multiply  the  weight 
in  tons  by  2,000. 

287.  Rated    Horsepower   of   Equipment.      The 
rated  horsepower  of  equipment  can  be  gotten  from 
the  number  of  motors  and  horsepower  per  motor, 
as  follows: — 

288.  Rule.     To  get  rated  horsepower  of  equip- 
ment from  number  of  motors  and  horsepower  per 
motor,    Multiply  the  number    of  motors  by  the 
horsepower  per  motor. 

289.  Example.     A  four-motor  car  has  40  horse- 
power motors.     What  is  the  rated  horsepower  of 
the  equipment? 

290.  Solution.     4  X  40  hp.  -  160  hp. 

291.  Rated  Full  Load  Current.     This  can  be 
gotten  as  follows: — 

292.  Rule.     To  get  the  rated  full  load  current 
of  equipment,  Multiply  horsepower  of  equipment 
by  746  and  divide  by  rated  voltage. 

293.  Example.     A  four-motor  car  has  40  hp. 
motors.     What  is  the  rated  full  current  load  of 
the  equipment  on  a  500- volt  service? 


102  MISCELLANEOUS  TESTS  OF 

294.  Solution.     4  X  40  =  160  hp. ;  and  160  X  746 
=  119,360  watts;    and  11 9, 360 -$-500  =  239  amp. 

295.  Note.     Should    the    motors   be    rated    at 
some  other  voltage  than  500  volts,  Divide  by  that 
rated  voltage  instead  of  500. 

296.  Duration  of  Test  (min.).    The  duration  of 
test  is  the  actual  time  required  to  make  the  trip 
less  unusual  delays  during  which  readings  were  not 
taken.      In   the   present   case,   the   total   duration 
(121  min.)  less  delays  en  route  and  at  terminals 
(18  min.),  leaves  103  min.  as  the  duration  of  the 
test. 

297.  Duration  of  Test  (hr.).     As  the  hour  is  the 
unit  used  in  calculations,  the  time  in  min.  is  reduced 
to  hr.,  as  follows: — 

298.  Rule.     To  reduce  the  duration  in  minutes 
to  duration  in  hours,  Divide  by  60. 

299.  Example.     The  duration  of  the  test  is  103 
min.    Wanted,  the  duration  in  hours. 

300.  Solution.     103  -f-  60  =  1.72  hrs. 

301.  Distance  Covered.     The  distance  covered 
can   be    gotten    from    the    operating   department 
where  it  is  used  in  making  up  time  tables;   if  not 
available,  it  can  be  derived  as  follows: — 

302.  Directions.     Start  two  men  from  opposite 
ends  of  the  route,  to  count  the  rails  in  one  side  of 
one  track ;  the  number  of  rails  X  2  gives  the  number 
of  end  on  rails  in  the  round  trip. 

303.  Rule.     To  get  the  distance  in  miles  from 
the  number  of  end  on  rails  in  one  rail  line,  Multiply 


ELECTRIC  CAR  EQUIPMENT  103 

the  feet  per  rail  by  the  number  of  rails  and  divide 
by  5,280. 

304.  Example.     A  test  route  includes  3,129.25, 
30  ft.  rails  in  one  rail  line.    What  is  the  distance  in 
miles? 

305.  Solution.     3,129.25x30  =  93,877.5  ft.;  and 
93,877.5-1-5,280=17.78  miles. 

306.  Note.     Rail  pieces  used  at  crossings  must 
be  reduced  to  lengths.     If  two  lengths  of  rails  are 
used,  note  the  number  of  each. 

307.  Number  of  Voltmeter  Readings.     As  the 
voltmeter  is  read  whether  there  is  current  or  not, 
the  number  of  voltmeter  readings  is  the  total  num- 
ber of  readings — in  this  case,  509,  and  their  sum  is 
262,095. 

308.  Average  Voltage.     The  average  voltage  is 
calculated  from  the  number  of  voltmeter  readings 
and  their  sum,  as  follows: — 

309.  Rule.     To  get  average  voltage  from  the 
sum  of  a  given  number  of  readings,  Divide  the  sum 
by  the  number. 

310.  Example.     The  number  of  voltmeter  read- 
ings being  509  and  their  sum  262,095,  what  was 
the  average  voltage  during  the  test? 

311.  Solution.     262,095  -*-  509  =  514  volts. 

312.  Maximum  and  Minimum  Voltages.     The 
maximum  voltage  is  the  highest  voltmeter  reading 
recorded;   the  minimum,  the  lowest,  unless  other- 
wise stated. 

313.  Note.     In     throwing     out     a     maximum 
reading  that  is  questionable,   the  next   highest  is 


104  MISCELLANEOUS  TESTS  OF 

taken  as  maximum.  In  throwing  out  a  minimum 
reading,  the  next  lowest  is  taken  as  minimum. 
Where  a  reading  is  thrown  out  it  must  be  ignored 
entirely. 

314.  Ammeter  and  Current  Readings.  509.    The 
ammeter  readings  include  the  0  current  readings : 
the  281  current  readings  do  not.    The  sum  of  the 
readings  is  the  same  in  both  cases — 43,773. 

315.  Average  Current-all  Readings.    The  aver- 
age current  of  all  readings  can  be  determined  from 
the  following  rule : — 

316.  Rule.     To  get  the  average  current  of  all 
readings,  Divide  the  sum  of  the  ammeter  readings 
by  their  number. 

317.  Example.     The  sum  of  the  ammeter  read- 
ings is  43,773  and  their  number  509.    Wanted,  the 
average  current  of  all  readings. 

318.  Solution.     43,773-5-509-86  amp. 

319.  Average  Current-current  Readings.     The 
average   current   of  the   current  readings  can   be 
gotten  from  the  following  rule: — 

320.  Rule.     To  get  the  average  current  of  the 
current  readings,  Divide  the  sum  of  the  current 
readings  by  the  number  of  current  readings. 

321.  Example.     The  sum  of  281  current  read- 
ings being  43,773,  What  is  the  average  current  of 
the*  current  readings? 

322.  Solution.     43,773  -*-  281  =  156  amp. 

323.  Note.    The  sum  of  the  ammeter  and  current 
readings  is  the  same,  because  adding  zeros  does  not 
increase  the  sum. 


ELECTRIC  CAR  EQUIPMENT  105 

324.  Maximum  Current.    The  maximum  current 
is  the  largest  ammeter  reading  recorded;  in  the 
present  case  it  was  355  amperes. 

325.  Note.     If  a  greater  current  is  known  to 
have  occurred  than  appears  on  the  test  record,  it 
can  be  noted  as  a  matter  of  information  but  must 
not  be  used  in  calculations. 

326.  Note.     Should  a  flash-over  or  other  abnor- 
mal condition  cause  excessive  current  while  taking 
a  reading,  Put  down  a  current  value  consistent  with 
preceding  and  following  values. 

327.  Maximum  Power  Reading.    The  maximum 
power  reading  is  the  largest  product  in  the  watts 
column  of  the  test  record — in  the  present  case, 
191,700  watts.    When  the  current  reading  is  0,  the 
power  reading  is  also  0,  because  the  power  reading 
is  the  product  of  the  volt  and  ampere  readings  and 
if  the  amperes  are  0  the  product  must  be. 

328.  Note.     In  the  present  test,  the  maximum 
power  and  current  readings  corresponded,  but  this 
is  but  a  coincidence,  as  the  voltage  corresponding 
to  a  lesser  current  might  easily  have  been  sufficiently 
greater  to  make  the  product  exceed  191,700. 

329.  Total  and  Actual  Power  Readings.     The 
total  number  of  power  readings,  509,  include  the 
zeros;  the  actual  power  readings,  281,  do  not.    The 
former  are  used  in  calculating  the  average  power  of 
all  readings ;  the  latter,  the  average  power  of  current 
readings. 

330.  Average  Power-all  Readings.    This  can  be 
calculated  as  follows: — 


106  MISCELLANEOUS  TESTS  OF 

331.  Ride.     To  get  the  average  power  of  all 
readings,  Divide  the  sum  of  the  power  readings  by 
the  total  number. 

332.  Example.     The  sum  of  509  power  readings 
is  21,851,395.     Wanted,  the  average  power  of  all 
power  readings. 

333.  Solution.     21,851,395-^-509  =  42,930  watts. 

334.  Average    Power-current    Readings.      The 
average   power   of   the   current   readings  may   be 
calculated  from  the  following  rule: — 

335.  Rule.     To  get  the  average  power  during 
the  actual  power  readings,  Divide  the  sum  of  the 
actual  readings  by  their  number. 

336.  Example.     The  sum  of  281  actual  power 
readings  is  21,851,395.    Wanted,  average  power  of 
actual  power  readings. 

337.  Solution.     21,851,395-^-281  =  77,763  watts. 

338.  Average  Speed.    The  average  speed  during 
the  test  can  be  determined  from  the  distance  in 
miles  and  the  time  in  hours. 

339.  Rule.     To    get    the    average    car    speed, 
Divide  the  distance  in  miles  by  the  time  in  hours 
required  to  traverse  it. 

340.  Example.     The    distance    traveled    in    a 
test  is  17.78  miles  and  the  time,  1.716  hours.  Want- 
ed the  average  speed  in  miles  per  hour. 

341.  Solution.     17.78  H- 1.716=  10.36  miles    per 
hour. 

342.  Note.     The  average  speed  seems  low,  but 
it  includes  the  time  consumed  by  frequent  stops — 
a  very  considerable  item. 


ELECTRIC  CAR  EQUIPMENT  107 

343.  Total  Energy  Absorbed  (watt-hours).    The 
total  energy  absorbed  is  the  average  rate  of  absorp- 
tion   (watts)  X  the   time    (hours)    during   which   it 
acted  and  is,  therefore,  expressed  in  watt-hours. 

344.  Rule.     To  get  the  watt-hours  absorbed, 
Multiply  the  time  in  hours  by  the  average  power 
in  watts  during  the  test. 

345.  Example.     The  average  power  is  42,930 
watts   and   the   duration,    1.716  hours.      Wanted, 
watt-hours  of  energy  absorbed. 

346.  Solution.     42,930  X  1.716  =  73,668    watt- 
hours. 

347.  Total  Energy  Absorbed  (kw.-hr.).    To  avoid 
large  numbers,  the  energy  unit  generally  employed 
is  the  kilowatt-hour  (kw.-hr.)  which  is  1,000  watt- 
hours.   It  is  gotten  from  the  watt-hours  as  follows : — 

348.  Rule.  To  convert  watt-hours  into  kilowatt- 
hours,  Divide  by  1,000. 

349.  Example.     Convert  73,668  watt-hours  into 
kilowatt-hours. 

350.  Solution.      73,668     watt-hours -J- 1 ,000  = 
73.668  kilowatt-hours. 

351.  Note.     To    convert    kilowatt-hours    into 
watt-hours,  Multiply  by  1,000. 

352 .  Total  Energy  Absorbed  (horsepower-hours) . 
Kilowatt-hours    are    converted    into    horsepower- 
hours  (hp.-hr.),  by  applying  the  following  rule: — 

353.  Rule.     To    convert    kilowatt-hours    into 
horsepower-hours,  Multiply  by  1.34. 

354.  Example.     Convert    77.668    kw.-hr.  into 
horsepower-hours. 


108  MISCELLANEOUS  TESTS  OF 

355.  Solution.    77.668  kw.-hr.  X  1.34=  104  hp.- 
hr. 

356.  Note.     To  convert  horsepower-hours  into 
kilowatt-hours,  Divide  by  1.34. 

357.  Example.     Convert  104  hp.-hr.  into  kilo- 
watt hours. 

358.  Solution.  104  hp.-hr. -4- 1.34  =  77.668  kw.-hr. 

359.  Average  Kilowatts.    To  compare  the  power 
required  by  different  equipments  over  the  same 
or  different  routes,  it  may  be  desirable  to  know  the 
average    kilowatts,    so  that  comparisons   may   be 
independent  of  the  durations  of  the  several  tests. 
In    railroad    work,    in    such    cases,    kilowatts    are 
generally  called  kilowatt-hours  per  hour,  both  units 
being  mathematically  the  same. 

360.  Rule.     To  get  the  average  kilowatts  or 
kilowatt-hours    per    hour   of   an    absorption    test, 
Divide  the  total  kilowatt-hours  by  the  time  in  hours. 

361.  Example.     The  total  kilowatt-hours  of  a 
test  are  73.66  and  duration,   1.716  hr.     Wanted, 
average  kilowatts  or  kilowatt-hours  per  hour  of  the 
test. 

362.  Solution.       73.66-5-1.716  =  42.93    kw.     or 
kw.-hr.  per  hr. 

363.  Kilowatt-hours  per  Mile.     The  kilowatt- 
hours  per  mile  are  obtained  as  follows: — 

364.  Rule.    To  get  the  kilowatt-hours  per  mile 
of  an  absorption  test,  Divide  the  total  kilowatt- 
hours  by  the  distance  covered  in  miles. 

365.  Example.     The  total  kilowatt-hours  ab- 


ELECTRIC  CAR  EQUIPMENT  109 

sorbed  is   73.66  and  the  distance  covered,  17.78 
miles.    Wanted,  the  kilowatt-hours  per  mile. 

366.  Solution.     73.66 -J- 17.78  =  4. 14  kw.-hr.  per 
mile. 

367.  Kilowatt-hours  per  Ton.    To  get  the  kilo- 
watt-hours per  ton,  in  an  absorption  test,  apply  the 
following  rule : — 

368.  Rule.    To  get  the  kilowatt-hours  per  ton, 
in  an  absorption  test,  Divide  the  total  kilowatt- 
hours  by  the  weight  of  the  car  in  tons. 

369.  Example.     The  weight  of  a  car  is  21.19 
tons  and  the  total  kilowatt-hours,  73.66.    What  is 
the  absorption  in  kilowatt-hours  per  ton? 

370.  Solution.    73.66-^21.19  =  3.47  kw.-hr.  per 
ton. 

371.  Kilowatts  per  Ton.      Kilowatt-hours  per 
ton  is  not  a  good  unit  for  comparing  tests,  unless 
they  have  the  same  duration.    A  better  basis  is  the 
kilowatts  per  ton  (or  kilowatt-hours  per  hour  per 
ton). 

372.  Rule.     To  get  the  average  kilowatts  per 
ton  (or  kilowatt-hours  per  hour  per  ton),  Divide 
the  total  kilowatt-hours  of  the  test  by  the  product 
of  the  duration  in  hours  and  the  car  weight  in  tons. 

373.  Example.      The    total    kilowatt-hours    is 
73.66,  the  duration,  1.716  hours  and  the  car  weight, 
21.19  tons.    Wanted,  the  kilowatts  per  ton. 

374.  Solution.    21.19X1.716  =  36.36;  and  73.66 
•+•  36. 36  =  2.02  kw.  per  ton  (or  kw.-hr.  per  hour  per 
ton). 


110  MISCELLANEOUS  TESTS  OF 

375.  Kw.-Hr.  per  Ton-mile.  The  kilowatt-hours 
of  energy  absorbed  per  mile  by  each  ton  of   car 
weight  can  be  calculated  as  follows: — 

376.  Rule.    To  get  the  average  kilowatt-hours 
per  ton-mile,  Divide  the  total  kilowatt-hours  by 
the  tons  car  weight  X  the  miles  traveled. 

377.  Example.     The   total   kilowatt-hours  are 
73.66;  the  distance,  17.78  miles;  the  weight,  21.19 
tons.    Wanted,  the  kilowatt-hours  per  ton-mile. 

378.  Solution.  21.19X17.78  =  376.75;  and  73.66 
-4-376.75  =  0.195  kw.-hr.  per  ton-mile. 

379.  Concluding    Remarks.       The    absorption 
test  is  more  instructive  if  the  per  cent,  of  all  grades 
along  the  route  is  determined  and  the  grades  named 
so  that  they  can  be  noted  as  they  are  reached ;  the 
watts  column  will  then  show  at  once  the  rate  of  ab- 
sorption due  to  different  per  cent,  grades. 

380.  The  average  voltage  of  the  test  is  514  volts; 
the  average  current,  86  amperes;    the  product  of 
these   average   values  is   44,204  watts,   which   is 
fairly  close  to  the  correct  result  of  multiplying 
together    corresponding    voltmeter    and    ammeter 
readings  and  averaging  the  products;   and  there  is 
temptation   to   use   the    shorter  but   meaningless 
method  of  obtaining  a  result  just  as  liable  to  be 
too  small  as  too  great. 

381.  The  voltmeter-ammeter  test  is  laborious, 
but  gives  more  information  on  voltage,  current  and 
incidents  than  a  wattmeter  test.  But  few  roads  have 
a  wattmeter  sufficiently  large  to  measure  the  energy 


ELECTRIC  CAR  EQUIPMENT  111 

absorbed  by  a  heavy,  four-motor  car.  Most  of 
them,  however,  have  voltmeters  and  ammeters 
the  capacities  of  which  can  be  sufficiently  increased 
by  multipliers  and  shunts. 


MISCELLANEOUS  TESTS 

SPEED  TESTS 

382.  Rail-count  Method.    An  approximate  speed 
test  depends  on  a  relation  between  the  number  of 
rails  traversed  per  second  and  the   car    speed  in 
miles  per  hour.    The  relation  is  as  follows: — 

383.  Rule.    The  number  of  30-ft.  rails  traversed 
by  a  car  in  20  sec.  is  the  speed  of  the  car  in  miles 
per  hour. 

384.  Example.    A  car  jounces  over  61  joints  in 
60  sec.  on  a  track  laid  with  30  ft.  rails.    Wanted, 
the  car  speed  in  miles  per  hour. 

385.  Solution.     As  1  joint  is  passed  before  a 
rail  has  been  traversed,  61  joints  in  60  sec.  is  60 
rails  in  60  sec.  or  one  rail  per  sec.  i.  e.,  20  rails  in  20 
sec.  or  a  speed  of  20  miles  per  hour. 

386.  Rule.     If  the  rails  are  60  ft.  long,  the  car 
speed  in  miles  per  hour  is  twice  the  number  of  rails 
traversed  in  20  sec.  or  number  of  rails  passed  in 
40  sec. 

387.  Example.    A  car  jounces  over  61  joints  in 
60  sec.  on  a  track  laid  with  60-ft.  rails.     Wanted, 
the  car  speed  in  miles  per  hour. 

388.  Solution.    61  joints  per  min.  is  60  rails  per 
min.  or  1  per  sec.  i.  e. ,  20  rails  in  20  sec. ;  2  X  20  =  40 
miles  per  hour. 

389.  Note.    Only  the  joints  on  one  side  are  to  be 
counted. 

112 


ELECTRIC  CAR  EQUIPMENT  113 

390.  Pole-count  Method.    Knowing  the  distance 
apart  of  the  line  poles  and  the  number  of  pole 
spaces  passed  in  1  minute,  the  car  speed  in  miles 
per  hour  can  be  determined  as  follows: — 

391.  Rule.    To  get  car  speed  in  miles  per  hour 
from  the  distance  apart  of  the  line  poles  and  the 
number  of  poles  passed  per  minute,  Subtract   1 
from  the  number  of  poles  per  minute  to  get  the 
number   of   spaces    per   minute.      Then   multiply 
together  the  number  of  spaces,  the  length  of  a 
space  in  feet  and  0.0113. 

392.  Example.     The  line  poles  average  112  ft. 
apart  and  a  car  passes  14.5  poles  per  min.    Wanted, 
the  car  speed  in  miles  per  hour. 

393.  Solution.     14.5-1  =  13.5;    and  13.5x112 
X0.0113=  17  miles  per  hour. 

394.  Minutes  per  Half-hour  Method.     To  find 
the  maximum  speed  attainable  on  level  track  at 
standard  voltage,  lay  off  a  half  mile,  mark  it  plainly 
and,  with  a  stopwatch,  take  the  time  required  by 
the  car  to  traverse  the  distance  between  the  marks, 
the  car  approaching  the  first  mark  at  full  speed; 
this  done,  the  speed  of  the  car  in  miles  per  hour  can 
be  calculated  by  the  following  rule: — 

395.  Rule.      To    get   car    speed   in   miles   per 
hour  from  the  time  (min.)  required  to  run  one-half 
mile,  Divide  30  by  the  time  in  minutes. 

396.  Example.     A  car  traverses  a  laid  off  half 
mile  in  1.5  minutes.    What  is  its  speed  in  miles  per 
hour? 

397.  Solution.    30  -*- 1  ^  =  20  miles  per  hr. 


114  MISCELLANEOUS  TESTS  OF 

398.  Note.      Motors    are    often   bought   under 
guarantee  to  run    a  car  of  given  weight  a  stated 
speed   at  standard  voltage.     This  test  should  be 
made  after  the  car  has  been  limbered  up  by  several 
days  of  operation.     If  the  speed  then  is  low,  See 
that  the  voltage  is  standard  and  that  the  controller 
operates  to  cut  out  all  resistance  on  the  last  parallel 
position. 

ACCELERATION  TESTS 

399.  Miles  per  Hour  per  Second.  (Miles  per  hr. 
per  sec.).      By   acceleration  is  meant   change   of 
speed  per  unit  of  time,  irrespective  of  whether  the 
change  is  an  increase  or  a  decrease.     Usage,  how- 
ever, accepts  acceleration  to  mean  increase  in  speed 
per  unit  of  time,  the  unit  of  time  generally  used 
being  the  second.     If  a  car  acquires  a  speed  of  15 
miles  per  hr.  from  rest,  the  gain  in  speed  is  15 
miles  per  hr. ;    but  before  the  acceleration  or  the 
rate  of  change  of  speed  can  be  expressed,  the  time  in 
seconds  required  to  make  the  gain  must  be  known. 
If  12  sec.  elapse  between  rest  and  a  speed  of  15 
miles   per  hour,    the   average   speed   increase   per 
second,  or  acceleration,   is  y1^  the  total  increase 
or  1.25  miles  per  hr.  per  sec. 

400.  Rule.    To  find  in  miles  per  hr.  per  sec.  the 
acceleration  from  rest  to  given  speed  acquired  in 
given  time,  Divide  the  miles  per  hour  speed  by  the 
time  in  seconds  required  to  attain  the  speed. 

401.  Example.     A  car  acquires  a  speed  of  16 
miles  per  hour  in  13  sec.    What  is  its  acceleration 
in  miles  per  hr.  per  second  ? 


ELECTRIC  CAR  EQUIPMENT  115 

402.  Solution.     16  miles  per  hr.  -r- 13  sec.  =  1.23 
miles  per  hr.  per  sec. 

403.  Feet  per  Second  per  Second.    Miles  per  hr. 
per  sec.  can  be  converted  into  ft.  per  sec.  per  sec.  by 
the  following  rule : — 

404.  Rule.     To  convert  miles  per  hr.  per  sec. 
into  ft.  per  sec.  per  sec.,  Multiply  the  miles  per  hr. 
per  sec.  by  1.47. 

405.  Example.     Convert  1.25  miles  per  hr.  per 
sec.  into  ft.  per  sec.  per  sec. 

406.  Solution.    1.25  miles  per  hr.  per  sec.  X  1.47 
=  1.83  ft.  per  sec.  per  sec. 

407.  Note.     To  convert  acceleration  in  ft.  per 
sec.  per  sec.  into  acceleration  in  miles  per  hr.  per 
sec.,  Divide  the  ft.  per  sec.  per  sec.  by  1.47. 

408.  Time     of     Acceleration.      The    time     of 
acceleration  can  be  obtained  as  follows: — 

409.  Directions.    To  get  the  time  of  accelerating 
a  car  from  rest  to  given  speed,  Connect  an  ammeter 
in  series  with  the  motor  circuit,  start  the  car  and  a 
stopwatch  simultaneously  and  stop  the  watch  the 
instant  the  steady  ammeter  needle  shows  the  speed 
to  be  uniform : — the  time  elapsed  on  the  watch  will 
be  the  time  of  acceleration  in  seconds. 

410.  Note.     The  time  test  should  be  repeated 
under  the  same  conditions  until  several  tests  check 
well  in  point  of  time. 

411.  Distance  of  Acceleration.    This  means  the 
rail  distance  covered  by  the  car  during  acceleration ; 
it  is  best  obtained  by  measuring  with  a  tape  line 


116  MISCELLANEOUS  TESTS  OF 

the  distance  between  the  initial  and  final  positions 
of  the  car  during  its  acceleration. 

412.  Average  Speed  of  Acceleration.    By  timing 
the     acceleration     and    measuring    the     distance 
covered  during  that  period,  the  average  speed  can  be 
determined  from  the  following  rule: — 

413.  Rule.     To  get  the  average  speed  during 
acceleration  in  ft.  per  sec.,  Divide  the  distance  of 
acceleration  in  feet  by  the  time  in  seconds.     Or 
multiply  the  acceleration  by  the  time  in  sec.  and 
divide  by  two. 

414.  Example.      In   accelerating   from   rest,   a 
car  travels  152  ft.  in  13  sec.    What  is  the  average 
speed  in  feet  per  second? 

415.  Solution.     152  ft.  -^  13  sec.  =  11. 69  ft.  per 
sec.    Or  1.80X13-5-2=11.7. 

416.  Note.     To  convert  ft.  per  sec.  into  miles 
per  hr.,  Divide  by  1.47.     To  convert  miles  per  hr. 
into  ft.  per  sec.,  Multiply  by  1.47. 

417.  Example.     An  average  speed  of  11.69  ft. 
per  sec.  =  how  many  miles  per  hr.? 

418.  Solution.     11.69  ft.  per  sec.  •*- 1.47  =  7.95 
miles  per  hr. 

419.  Example.    Convert  7.95  miles  per  hr.  into 
speed  in  ft.  per  sec. 

420.  Solution.    7.95  miles  per  hr.  X  1.47=  11.69 
ft.  per  sec. 

421.  Maximum  Speed  of  Acceleration.    This  can 
be  gotten  as  follows: — 


ELECTRIC  CAR  EQUIPMENT  117 

422.  Rule.    To  get  the  maximum  speed  due  to 
acceleration  of  a  car  started  from  rest,  Multiply 
the  average  speed  of  acceleration  by  two.     The 
maximum  speed  will  be  in  the  same  units  as  average 
speed. 

423.  Example.     The   average  speed  of  a   car 
during  acceleration  is   11.69  ft.   per  sec.   or  7.95 
miles  per  hr.     Wanted,  (a)  maximum  speed  in  ft. 
per  sec.  and  (b)  in  miles  per  hour. 

424.  Solution,     (a)  11.69  ft.  per  sec.  X2  =  23.38 
ft.   per  sec.  and  (b)  7. 95  miles  per  hour X2=  15.9 
miles  per  hour. 

425.  Proof.    From  Note  of  Art.  416,  15.9  miles 
per  hr.  X  1.47  =  23.38  ft.  per  sec. 

426.  Note.     To  get  the  average  speed  of  accel- 
eration from  the  maximum  speed  of  acceleration, 
Divide  the  maximum  speed  by  two. 

427.  Force   of  Acceleration.     This  means  the 
force  in  pounds  to  be  applied  as  a  push  or  pull  in 
the  direction  of  motion,  to  produce  a  given  accelera- 
tion in  miles  per  hr.  per  sec.  or  ft.  per  sec.  per  sec. 

428.  Rule.    To  get  the  force  in  pounds  required 
to  accelerate  a  car  of  given  weight  in  tons  at  a  given 
rate  in  miles  per  hr.  per  sec.,  Multiply  the  product 
of  the  weight  and  acceleration  by  91.2. 

429.  Example.    A  10-ton  car  is  to  be  given  an 
acceleration  of  1.23  miles  per  hr.  per  sec.     What 
force  will  be  required? 

430.  Solution.    10X1.23X91.2  =  1,122  Ib. 

431.  Where,  the  acceleration  is  given  in  ft.  per 


118  MISCELLANEOUS  TESTS  OP 

sec.  per  sec.,  the  force  of  acceleration  can  be  gotten 
from  the  following  rule : — 

432.  Rule.    To  get  the  force  in  pounds  required 
to  produce  a  given  acceleration  in  ft.  per  sec.  per 
sec.   of  a  car  of  given  weight  in   tons,   Multiply 
together  the  weight,  acceleration  and  62.32. 

433.  Example.    A  10-ton  car  is  to  be  accelerated 
1.8  ft.  per  sec.  per  sec.    Wanted,  the  force  required 
to  produce  this  acceleration. 

434.  Solution.     10x1.8x62.32  =  1,122  Ib. 

435.  Horsepower  of  Acceleration.     This  means 
the   horsepower   required   to   accelerate   a   car   to 
given    speed,   independently    of    the    horsepower 
expended  in  overcoming  f fictional  resistances,  to  be 
considered  later. 

436.  Rule.    To  get  the  horsepower  of  accelera- 
tion, Multiply  the  force  of  acceleration  (Ib.)  by  the 
distance    (ft.)    and   divide   by   550  X the   time   in 
seconds. 

437.  Example.    A  force  of  1,122  Ib.  accelerates 
a  car  to  full  speed  in  13  sec.  over  a  distance  of  152 
ft.    At  what  hp.  i.  e.,  rate,  was  energy  expended  in 
accelerating  the  car? 

438.  Solution.     1,122x152=170,544;    and  550 
X13  =  7,150;  and  170,544-^7,150  =  23.8  hp. 

439.  Note.    As  electric  cars  are  not  accelerated 
at  a  uniform  rate,  owing  to  resistances  being  cut  out 
in  impulses,  the  force  acting  during  acceleration  is 
not  constant;    the  calculated  force  is,   then,   the 


ELECTRIC  CAR  EQUIPMENT  119 

average  force  of  acceleration  and  the  calculated  hp. 
the  average  hp.  during  acceleration. 

RETARDATION  TESTS 

440.  Introductory  Remarks.    Retardation  means 
rate  of  decrease  in  speed  and  is  here  understood  to 
be  due  to  the  car  brake.    With  an  air-brake  in  good 
order,  it  is  comparatively  easy  to  measure  the  time 
elapsing  between  the  application  of  the  brake  and 
the  stopping   of  the   car,  because  air-brakes  act 
promptly  on  operating  the  motorman's  valve  to 
admit  air  to  the  brake  cylinder.    On  a  hand-braked 
car,  however,  the  time  elapsing  depends  more  on 
the  condition  and  effectiveness  of  the  rigging  and 
the  effort  of  the  brakeman,  so  that  reliable  results 
are  to  be  gotten  only  by  having  lost  motion  and 
clearance  a  minimum  and  by  repeating  tests  until 
results    check.      An    air-brake    applies   maximum 
braking  force  initially  when  the  car  speed  is  greatest 
and  the  liability  to  lock  wheels  least ;  a  hand-brake 
applies  the  braking  force  at  a  gradually  increasing 
rate,  owing  to  the  time  required  to  bring  it  into 
action. 

441.  Miles  per  Hour  per  Second.    The  retarda- 
tion in  miles  per  hr.  per  sec.  can  be  determined  as 
follows : — 

442.  Directions.    To  determine  the  retardation 
of  a  car  in  miles  per  hr.  per  sec.,  Bring  the  car  to 
uniform  speed,  as  indicated  by  an  ammeter  in  the 
motor  circuit,  on  level  track;    at  a  given  signal, 
start  a  stop-watch  and  apply  the  brake ;  the  instant 


120  MISCELLANEOUS  TESTS  OF 

the  car  stops,  stop  the  watch  and  note  the  position 
of  the  car.  Repeat  the  test  several  times  under  the 
same  conditions,  each  time  carefully  noting  the 
initial  and  final  positions  of  the  car,  so  that  the 
distance  of  retardation  can  be  measured.  Having 
the  distance  in  miles  and  the  time  in  seconds,  the 
retardation  in  miles  per  hr.  per  sec.  can  be  deter- 
mined as  follows: — 

443.  Rule.    To   get   retardation    in  miles    per 
hr.  per  sec.  from  maximum  speed  in  miles  per  hr. 
and  time,  in  seconds,  Divide  the  speed  by  the  time. 

444.  Example.     A  car  running  at  16  miles  per 
hr.  is  brought  to  a  stop  in  11  sec.     Wanted,  the 
retardation  in  miles  per  hr.  per  sec. 

445.  Solution.     16  miles  per  hr.  -»- 11  sec.  =  1.45 
miles  per  hr.  per  sec. 

446.  Feet  per  Second  per  Second.    Miles  per  hr. 
per  sec.  can  be  converted  into  ft.  per  sec.  per  sec. 
by  applying  the  following  rule : — 

447.  Rule.    To  convert  retardation  in  miles  per 
hr.  per  sec.  into  retardation  in  ft.  per  sec.  per  sec. , 
Multiply  by  1.47. 

448.  Example.    The  retardation  of  a  car  is  1.45 
miles  per  hr.  per  sec.    Express  this  retardation  as 
ft.  per  sec.  per  sec. 

449.  Solution.    1.45  X  1.47  =  2. 13  ft.  per  sec.  per 
sec. 

450.  Note.     As  in  the  case  of  acceleration  to 
convert  ft.  per  sec.  per  sec.  into  miles  per  hr.  per 
sec.,  Divide  by  1.47. 


ELECTRIC  CAR  EQUIPMENT  121 

451.  Distance  of  Retardation.    This  means  the 
length  of  rail  covered  during  retardation  and  is  best 
gotten  by  actual  measurement,  with  a  tape  line, 
between  the  positions  of  the  car,  when  starting  the 
stop-watch  and  stopping  it. 

452.  Average  Speed  During  Retardation.     This 
can  be  gotten  from  time  and  distance  of  retardation 
by  substituting  retardation  for  acceleration  in  the 
rule  of  Art.  413  or  divide  the  speed  of  the  car 
by  two. 

453.  Example.    A  car  is  brought  from  maximum 
speed  to  rest  in  11  sec.,  traversing  128.7  ft.    Wanted 
average  speed  during  retardation. 

454.  Solution.      128.7-5-11  =  11.7;     and    11. 7  X 
1.47  =  8  miles  per  hr.  or  16^-2  =  8. 

455.  Maximum     Speed     During     Retardation. 
This  is  the  speed  existing  at  the  time  of  applying 
the  brake  in  the  retardation  test  and  can  be  gotten 
by  applying  the  rule  of  Art.  422. 

456.  Example.    The  average  speed  during  retar- 
dation being  8  miles  per  hr. ,  wanted  the  maximum 
speed  during  retardation  in  miles  per  hr. 

457.  Solution.    8  miles  per  hr.  X 2=  16  miles  per 
hr.,  maximum  speed. 

458.  Concluding  Remarks.    Under  similar  condi- 
tions a  car  can  be  retarded  from  given  speed  to  rest 
in  less  time  and  distance  than  it  can  be  accelerated 
from  rest  to  that  same  speed,  because  (a)  all  f fic- 
tional forces  help  retardation  but  oppose  accelera- 
tion;   (b)  where  controllers  have  but  few  notches, 
accelerating  force  cannot  be  applied  to  as  good 


122  MISCELLANEOUS  TESTS  OF 

advantage  as  can  the  retarding  force  due  to  a  good 
brake. 

459.  Acceleration  tests  may  be  run  to  determine 
the  smoothness  of  controller  notching  for  the  purpose 
of  improving  it  so  as  to  get  quick,  smooth  starting, 
to  save  time.     In  service  that  has  frequent  stops, 
the  time  lost  in  poor  acceleration  is  considerable, 
and  the  motormen's  efforts  to  compensate  for  it 
by  rapid  notching,  invite  accidents.    The  same  can 
be  said  of  retardation  as  related  to  badly  designed 
or  poorly  maintained  brakes.    In  addition,  retarda- 
tion tests  may  be  run  to  determine  the  relative 
effectiveness  of  different  makes  or  types  of  shoes  or 
riggings;   or  such  tests  may  be  made  on  particular 
cars  that  have  been  involved  in  an  accident,  to 
determine  the  minimum  distance  in  which  the  car 
might  have  been  stopped. 

TRAIN  RESISTANCE 

460.  Introductory  Remarks.     Train  resistance 
is  the  opposition  of  various  forms  of  friction  to 
train  motion.    If  a  car  is  raised  to  speed,  the  power 
turned  off  and  the  car  permitted  to  roll  along  or 
coast,  train  resistance  will,  in  time,  stop  the  car  un- 
less it  is  on  the  down  grade;   on  an  up  grade,  the 
car  will  stop  sooner,  but  then  the  stop  is  due  to 
combined    grade    and    train    resistance.      Except 
for  grades,  train  resistance  is  the  only  retarding 
agent  to  be  overcome  by  the  motors,  and  were  it 
not  for  train  resistance,  a  car  once  started  on  level 
track     would    run    on    at     undiminished     speed 


ELECTRIC  CAR  EQUIPMENT  123 

without  any  further  application  of  motive  power. 

461.  Measurement  on  Level  Track.    This  meas- 
urement requires  about  1,000  ft.  of  straight,  level 
track;   it  is  made  as  follows: — 

462.  Directions.    To  measure  train  resistance  on 
level  track,  Accelerate  the  car  to  full  speed,  as  indi- 
cated by  an  ammeter;   at  a  given  signal,  throw  off 
the  power,  start  the  watch,  note  the  position  of  the 
car,  allow  it  to  coast  to  rest,  stop  the  watch  and 
again  note  the  position  of  the  car.     Knowing  the 
distance  (ft.)  and  time  (sec.)  of  coasting,  the  aver- 
age speed  is  determined  from    the    rule   of    Art. 
413  and    the   maximum   speed  from   the  rule  of 
Art.  422. 

463.  Knowing  the  maximum  speed  in  ft.  per 
sec.,  the  distance  in  feet  and   the  car- weight   in 
pounds,  the  train  resistance  is  gotten  as  follows: — 

464.  Rule.     To  calculate  total  train  resistance 
from  maximum  speed,  distance  traversed  in  coast- 
ing and  car- weight,  Divide  the  car- weight  in  pounds 
by  32  and  multiply  by  the  square  of  the  speed  in 
ft.  per  sec. ;  then  divide  by  twice  the  distance  in  feet. 
The  result  will  be  the  total  train  resistance  in 
pounds. 

465.  Example.    Train  resistance  alone  brings  a 
20-ton  car  from  full  speed  to  rest  in  58.6  sec.,  the 
coasting  distance  traversed  being  688  ft.    Wanted, 
the  total  train  resistance. 

466.  Solution.      40,000-7-32=1,250;   from   the 
rule  of   Art.    413,    688  ft. -f- 58.6    sec.  =  11.728  ft. 
per  sec.,  average  speed;  from  the  rule  of  Art.  422, 


124  MISCELLANEOUS  TESTS  OF 

11.728X2  =  23.456  ft.  per  sec.,  maximum  speed; 
23.456X23.456=550.18,  square  of  speed;  550. 18 X 
1,250  =  687,725;  2x688  ft.  =  1,376  ft.,  twice  the 
distance;  687, 725 -*•  1,376  =  500  lb.,  total  train 
resistance. 

467.  Note.    The  term  train  resistance  generally 
refers  to  the  resistance  per  ton.     To  get  the  train 
resistance  per  ton  from  the  total  train  resistance 
and  the  car  weight  in  tons,  Divide  the  total  train 
resistance   by    the    number   of   tons.      The    train 
resistance  per  ton  in  the  last  example  is  500  lb.-^  20 
=  251b. 

468.  Measurement  on  Grades.    On  a  grade,  the 
difference  in  level  between  the  points  where  coast- 
ing starts  and  the  car  stops  must  be  known,  so  that 
the  retarding  effect  of  the  grade  can  be  calculated 
and  deducted.      Knowing  the   distance  in  which 
train  resistance  and  the  grade  stop  the  car  and  the 
distance  through  which  the  car  is  raised  by  the 
grade,  the  retarding  effect  of  the  grade  can  be 
calculated  as  follows : — 

469.  Rule.    To  get  the  retarding  resistance  of  a 
grade  on  a  car  of  given  weight  in  pounds,  Multiply 
the  car-weight  in  pounds  by  the  distance  raised  in 
feet,  and  divide  by  the  coasting  distance  in  feet. 
The  result  will  be  the  grade  resistance  in  pounds. 

470.  Example.      Combined    train    and    grade 
resistances  bring  a  40,000-lb.  car  from  16  miles  per 
hr.  to  rest  in  344  ft.,  the  rise  being  4.3  ft.    Wanted, 
the  train  and  grade  resistance  per  ton. 

471.  Solution.      From   the  rule   of   Art.   464, 


ELECTRIC  CAR  EQUIPMENT  125 

40,000-^32  =  1,250;  23.456X23.456  =  550.18;  550.18 
X  1,250  =  687,725;  687,725-^-688=1,000  lb.,  com- 
bined train  and  grade  resistances;  from  the  rule 
of  Art.  469,  40,000x4.3=172,000  ;  172,000-344  = 
500  lb.,  total  resistance  of  grade;  1,000  lb.  -oOOlb. 
=  500  lb. ,  total  train  resistance ;  500  lb.  -f-  20  =  25  lb. , 
train  resistance  per  ton;  500  lb.  -=-20  =  25  lb.,  grade 
resistance  per  ton. 

472.  Note.     The   apparent   train   resistance  is 
calculated  as  if  no  grade  existed  (Rule  of  Art.  464). 
The  grade  resistance  is  then  calculated  by  the  rule 
of  Art  469  and  subtracted  from  the  apparent  train 
resistance,  to  get  the  total  train  resistance. 

HORSEPOWER  OF  TRACTION 

473.  Introductory    Remarks.      Horsepower    oi 
traction  here  means  average  rate  at  which  energy 
must  be  absorbed  to  carry  a  car  of  given  weight  a 
given  distance  in  a  given  time.     Two  cases  will  be 
be  considered: — 

1.  On  level  track  where  only  train  resistance 
opposes  movement. 

2.  On  grades  where  grade  resistance  has  retard- 
ing effect. 

474.  Ft.    per  Sec.    Method   on   Levels.      Given 
train  resistance  in  pounds  per  ton,  car  speed  in  ft. 
per    sec.    and     car-weight    in    pounds,    calculate 
horsepower   as   follows : — 

475.  Rule.     To  get  the  average  horsepower  of 
traction  of  a  car  of  given  weight,  at  given  speed, 
against  given  train  resistance  per  ton,   Multiply 


126  MISCELLANEOUS  TESTS  OF 

together  weight  of  car  in  tons,    speed  and  train 
resistance  per  ton  and  divide  by  550. 

476.  Example.    A  20-ton  car  runs  16  miles  per 
hr.  on  a  level  against  a  train  resistance  of  25  Ib.  per 
ton.    Wanted,  the  average  horsepower  absorbed. 

477.  Solution.     From  the  note  of  Art.  416,  16 
miles  per  hr.  X  1.47  =  23.5  ft.  per  sec.       From  the 
rule    of   Article  475,  20x25  lb.  =  500  Ib.;    500 X 
23.5=11,750    ft.-lb.   per  sec.;  and    11,750-550  = 
21.3,  average  horsepower  absorption. 

478.  Miles  per  Hr.  Method  on  Levels.    Given  car 
weight  in  tons,  speed  in  miles  per  hr.  and  train 
resistance  in  pounds  per  ton,  the  average  horse- 
power of  traction  can  be  calculated  from  the  follow- 
ing rule : — 

479.  Rule.     To  get  the  average  horsepower  of 
traction  of  a  car  of  given  weight,  at  given  speed, 
against  given  train  resistance   (Ib.  per  ton)  on  a 
level,   Multiply  the  car- weight  in  tons,  speed  and 
train  resistance  and  divide  by  375. 

480.  Example.    What  is  the  average  horsepower 
required  to  run  a  20-ton  car  at  16  miles  per  hr. 
against  a  train  resistance  of  25  Ib.  per  ton  ? 

481.  Solution.       16x20x25  =  8,000;      8,000- 
375  =  21.3  horsepower. 

482.  Calculation  of  Grade  Effect.     To  find  the 
horsepower  required  to  take  a  car  of  given  weight 
up  a  given  grade,  at  given  uniform  speed,  the  train 
resistance  per  ton  being  known,  the  horsepower  of 
train  resistance  is  calculated  by  the  rule   of   Art. 
475  and  to  it  is  added  the  horsepower  required  to 


ELECTRIC  CAR  EQUIPMENT  127 

overcome  the  grade.  To  calculate  the  horsepower 
necessary  to  overcome  the  grade,  the  net  rise  or 
rise  per  ft.  of  track  must  be  known. 

483.  Rule.    To  get  the  horsepower  required  to 
run  a  car  of  given  weight  (lb.),  at  given  uniform 
speed  (ft.  per  sec.)  up  a  grade  of  given  rise  per  foot, 
Multiply  the  car- weight,  the  rise  per  foot  and  the 
speed  together,  then  divide  by  550. 

484.  Example.      Wanted,   the   horsepower   re- 
quired to  impel  a  20-ton  car  up  a  grade  that  rises 
0.0125  ft.  in  1  ft.,  against  a  train  resistance  of  25 
lb.  per  ton  and  at  a  speed  of  16  miles  per  hr. 

485.  Solution.     From  the  rule  of  Art.  475  the 
horsepower  required   to  overcome  train  resistance 
is  21. 3;     from    the    rule    of    Art.    483,    40, 000  X 
0.0125  =  500;     500x23.5=11,750;    11,750-1-550  = 
21.3   horsepower    to    overcome    the    grade.     21.3 
horsepower  +  21.3  hp.  =  42.6  hp. 

486.  Calculation  of  Grade  Rise.    The  per  cent, 
rise  of  grade  is  the  distance  that  a  car  is  raised  in 
traveling  100  ft.  on  the  grade.     Thus  on  a  6  per 
cent,  grade,  a  car  running  100  ft.  on  the  rail  would 
be  raised  6  ft.    The  distance  that  a  car  is  raised  by 
traveling  a  given  distance  on  a  grade  of  given  per 
cent,  can  be  gotten  as  follows: — 

487.  Rule.    To  get  the  rise  in  feet  for  a  given 
rail  distance  in  feet  on  a  grade  of  given  per  cent., 
Multiply  the  rail  distance  in  feet  by  the  per  cent,  of 
the  grade  and  divide  by  100. 

488.  Example.    A  car  runs  344  ft.  on  a  1.25  per 


128  MISCELLANEOUS  TESTS  OF 

cent,  grade.   Through  what  vertical  distance  is  the 
car  raised  by  the  grade? 

489.  Solution.    344x1.25  =  430;   and  430  H- 100 
=  4. 3  ft. 

490.  Calculation  of  Per  Cent  Grade.     Knowing 
the  rail  length  of  the  grade  and  the  rise  from  end  to 
end,  the  per  cent,  of  the  grade  can  be  calculated 
from  the  following  rule : — 

491.  Rule.    To  get  the  per  cent,  of  a  grade  from 
its  rise  and  length  along  the  rail,  Divide  100  X rise 
(ft.)  by  rail  distance  in  feet. 

492.  Example.    The  rail  length  of  a  grade  being 
344  ft.  and  its  rise,  4.3  ft.,  wanted  the  per  cent,  of 
the  grade. 

493.  Solution.     100x4.3  =  430;    and  430-344 
=  1.25  per  cent. 

494.  Note.    As  a  rule  the  grade  rise  is  determined 
with  an  engineer's  level,  but  it  can  be  approximated 
by  sighting  over  the  tops  of  rods  of  different  lengths. 

TOTAL  HORSEPOWER  OF  OPERATION 

495.  The    horsepower    required    to    overcome 
train,  grade  and  acceleration  resistances  have  been 
considered.     The  horsepower  required  to  overcome 
the  simultaneous  effects  of  all  is  here  called  the 
total  horsepower  of  operation;  it  can  be  calculated 
as  follows: — 

496.  Rule.       To    find    the     total     horsepower 
required  to  overcome  specified  conditions  of  train 
resistance,  grade,  acceleration:  calculate  the  horse- 
power of  train  resistance  by  the  rule  of  Art.  479, 


ELECTRIC  CAR  EQUIPMENT  129 

the  horsepower  of  acceleration,  by  the  Rules  of 
Arts.  428  and  436  and  the  horsepower  of  the 
grade  by  the  rule  of  Art.  483;  then  add  these 
values  to  get  the  total  horsepower  of  operation. 

497.  Example.     Wanted,  the  total  horsepower 
of  operation  required  to  accelerate  a  20-ton  car 
1.23  miles  per  hr.  per  sec.  on  a  1.25  per  cent,  grade, 
against  a  train  resistance  of  25  Ib.  per  ton;    the 
final  speed  to  be  16  miles  per  hr. 

498.  Solution.     From  the  rule  of  Art.  479, 16  X 
20X25  =  8,000;      and     8,000-375  =  21.3,    average 
horsepower     required     to      overcome     the     train 
resistance. 

From  the  rule  of  Art.  428,  20x1.23x91.2  = 
2,243.52  Ib.,  force  of  acceleration  required.  From 
the  rule  of  Art.  436,  2,243.52  lb.Xl52  ft.  =  341,- 
015ft.-lb.;  and  550x13  =  7,150;  and  341,015^-7,- 
150  =  47.6  hp.  required  to  overcome  the  resistance 
of  acceleration. 

From  the  rule  of  Art.  483,  40,000  Ib.  X0.0125 
ft.  =  500  ft.-lb.,  the  total  work  done  per  rail-ft.  of 
grade;  500x11.7  ft.  per  sec.  =  5,850  ft.-lb.  of  work 
done  per  second;  5,850  —  550=10.6  hp.  required 
to  overcome  the  grade. 

21.3  hp.  +  47.6  hp.  +  10.6  hp.  =  79.5  hp.,  total. 

499.  Note.     The  152  ft.  is  gotten  by  multiply- 
ing the  11.7,  average  speed  in  ft.  per  sec.,  by  13  sec., 
the  time  of  acceleration. 

500.  Note.    The  time  of  acceleration,  13  sec.,  is 
gotten  by  dividing  the  maximum  speed,  16  miles 


130  MISCELLANEOUS  TESTS  OF 

per  hr.  by  the  acceleration,  1.23  miles  per  hr.  per 
sec. 

501.     Note.    The  rise  per  foot  of  a  1.25  per  cent, 
grade  is  0.0125  ft. 


HELP  TO  THE  INJURED 

REVIVING  SHOCKED  PERSONS 

502.  The  following  directions  for  reviving  per- 
sons from  the  effects  of  electric  shock  (or  apparent 
drowning)  are  due  in  substance  to  Augustin 
Goelet,  M.D.,  and  are  adapted  from  the  Electrical 
World  and  Engineer  of  September  6,  1902.  In  all 
cases  the  operations  described  are  to  be  begun 
without  delay  and  continued  until  the  arrival  of 
a  physician. 


503.  Directions.  I.  Remove  the  body  from  the 
live  conductor ;  if  in  mid  air,  poke  it  loose  with  a 
wooden  pole  and  catch  it  in  a  blanket  held  at  the 
four  corners,  unless  there  are  present  facilities  and 
persons  qualified  safely  to  use  more  refined  meth- 
ods. If  on  the  surface,  use  a  dry  stick  or  protect 
the  hands  with  dry  clothing. 
131 


132  MISCELLANEOUS  TESTS  OF 

II.  Turn  the  body  upon  the  back,  loosen  the 
clothing  around  the  neck  and  chest  and  waist  and 
place  a  rolled  up  coat  under  the  shoulders  to  throw 
the  head  back  and  mouth  open.  Kneeling  at  the 
victim's  head,  seize  both  arms  and  draw  them  to 
full  length  and  almost  together  over  the  head,  as 
in  Fig.  72,  to  expand  the  chest  and  open  the  wind- 
pipe; hold  this  position  for  two  or  three  seconds; 
next  carry  the  arms  down  to  the  sides,  Fig.  73  show- 
ing the  halfway  position , and  front  of  the  chest ,  firmly 
compressing  the  chest  walls,  as  indicated  in  Fig.  74, 


FIG.  73 

to  expel  the  air  from  the  lungs.  These  successive 
operations  of  drawing  the  arms  back  over  the  head 
almost  together  and  then  bending  them  as  in  Fig.  73, 
and  finally  compressing  them  on  the  chest  side 
walls,  as  in  Fig.  74,  must  be  repeated  from  sixteen 
to  eighteen  times  per  minute  and  continued  cease- 
lessly for  at  least  an  hour  or  until  the  breathing  is 
normal.  (This  method  has  been  known  to  resusci- 
tate patients  who  had  been  under  water  several 
hours.) 


ELECTRIC  CAR  EQUIPMENT  133 

III.  While  artificial  breathing  is  being  thus  con- 
ducted, a  second  person  should  grasp  the  patient's 
tongue  with  a  handkerchief  (forcing  the  teeth 
apart  with  a  knife  or  piece  of  wood,  if  necessary) 
and  pull  the  tongue  out  in  step  with  the  stretching 
of  the  arms  and  allowing  it  to  recede  into  the  mouth 
when  the  chest  is  compressed. 


FIG.  74 

504.  Note.  Dashing  cold  water  in  the  face, 
brisk  rubbing  of  the  spine  with  ice  or  alternate 
heating  and  cooling  of  the  region  over  the  heart  all 
tend  to  produce  a  gasp  and  thereby  start  breathing, 
which  should  then  be  continued  artificially,  until 
it  becomes  natural.  It  is  both  useless  and  unwise 
to  try  to  revive  the  patient  by  pouring  stimulants 
down  the  throat.  In  all  cases  SEND  FOR  A 
PHYSICIAN. 

RELIEVING  BURNS 

506.  The  simplest  and  most  satisfactory  relief 
for  an  electric  burn  is  to  immerse  the  affected  part 
in  a  mixture  of  linseed  oil  and  soda  and  to  keep  it 


134  MISCELLANEOUS  TESTS  OF 

there  until  all  soreness  is  gone.  Where  numbers  of 
men  are  employed,  a  barrel  of  this  mixture  should 
be  kept  on  hand.  In  case  of  severe  body  burns,  the 
body  can  be  wrapped  in  bandages  to  be  kept 
saturated  with  the  oil  and  soda  mixture.  In 
emergencies,  the  patient  can  be  stood  in  the  barrel. 


REHEARSAL   QUESTIONS 

1 .  How  does  height  of  trolley  wire  affect  trolley  pressure? 

2.  In  what  locations  is  the  pressure  apt  to  be  excessive? 

3.  In  what  locations  is  it  likely  to  be  deficient? 

4.  Why  is  wheel  jumping  at  steam  crossings  dangerous? 

5.  What  is  the  object  of  the  rough  pressure  test? 

6.  How  is  the  rough  pressure  test  conducted? 

7.  Can  a  spring  scale  be  applied  to  pressure  testing? 

How? 

8.  At  what  angle  is  the  scale  preferably  applied? 

9.  What  is  the  advantage  of  applying  the  scale  verti- 

cally? 

10.  Why  does  the  vertical  pull  exceed  that  at  right  angles? 

11.  Why  should  the  stretch  of  test  wire  be  free  from  sag? 

12.  What  is  meant  by  the  pole-roof  angle  of  a  trolley 

pole? 

13.  Is  trolley  pressure  affected  by  length  of  pole?   Height 

of  car? 

14.  Why  do  the  pressures  vary  on  similar  cars  in  like 

service? 

15.  What  are  the  effects  of  excessive  trolley  pressure? 

16.  State  the  effects  of  deficient  trolley  pressure. 

17.  Why  does  pressure  required  vary  with  the  car  speed? 

18.  How  may  the  most  desirable  pressure  be  determined? 

19.  Of  what  does  a  car  house  plow  pressure  test  consist? 

20.  Describe  the  shop  pressure  test  for  electric  plows. 

21.  What  would  be  the  effect  of  excessive  plow  shoe 

pressure? 

22.  What  would  be  the   effect  of  deficient   plow   shoe 

pressure  ? 

23.  What  is  the  approximate  pressure  per  square  inch  on 

plow  shoes? 

24.  What  is  meant  by  instantaneous  blowing  test  of  a 

fuse? 

135 


136  MISCELLANEOUS  TESTS  OF 

25.  What  is  meant  by  the  time  element  blowing  test  of  a 

fuse? 

26.  Where  can  such  a  test  be  used  to  advantage? 

27.  What  is  meant  by  the  operating  test  of  a  fuse? 

28.  State  the  disadvantage  if  a  fuse  is  too  large.     Too 

small. 

29.  Should  cars  of  different  weights  and  capacities  be 

fused  alike? 

30.  State  a  rule  for  finding  the  size  of  a  copper  fuse. 

31.  Give  several  reasons  that  justify  the  use  of  copper 

fuses? 

32.  What  conditions  affect  the  capacity  of  a  fuse? 

33.  State  the  advantages  of  circuit  breaker  adjustments? 

34.  Does    breaker     adjustment     decrease     the     current 

demand  per  car? 

35.  Does    it    educate    motormen    to    careful    controller 

handling? 

36.  Describe  the  limit  circuit  breaker  test. 

37.  What  is  the  disadvantage  of  the  ammeter  breaker 

test? 

38.  Give  the  dimensions  of  a  useful  size  of  water  rheostat. 

39.  What  is  the   advantage   of  liberal   cross-section  of 

water? 

40.  How    may    the    resistance    of  water  be  decreased? 

Increased? 

41.  Why  may  a  barrel  not  be  used  indoors  as  a  rheostat? 

42.  Give    one    method    of    attaching    test   lines    to    car 

breakers. 

43.  Name  the  requirements  of  the  controller  cylinder 

interlocks. 

44.  State  the  danger  of  reversing  a  car  with  the  power  on. 

45.  Why  are   reverse  handles  made  unremovable  with 

power  on? 

46.  Why  are  main  cylinders  immovable  with  the  reverse 

"off"? 

47.  How  can  opposite   reverses  be  maliciously  turned 

oppositely? 


ELECTRIC  CAR  EQUIPMENT  137 

48.  Why  should  there  be  but  one  reverse  handle  to  a  car? 

49.  What  is  the  object  of  the  main  cylinder  interference? 

50.  With  the  interference  out  of  order,  what  may  happen? 

51.  What   is   meant   by   vertical   alinement   of   fingers? 

Horizontal  ? 

52.  How  can  the  alinements  be  tested?     Define  notch 

spacing. 

53.  To  what  may  incorrect  notch  spacing  be  due?    State 

effects. 

54.  What  indications  fix  notch  spacing  defects  in  the 

cylinder? 

55.  What  is  the  object  of  controller  open  circuit  test? 

How  made? 

56.  What  knowledge  is  required  to  make  such  a  test? 

57.  In  the  absence  of  such  knowledge  what  aid  is  neces- 

sary? 

58.  What  is  meant  by  a  controller  complete  circuit  test? 

59.  Describe  the  method  of  making  such  a  test  on  the 

bench. 

60.  Describe  the  controller  short-circuit  test. 

61.  Is  a  ground  fault  a  special  case  of  short-circuit? 

62.  What  testing  precautions  must  be  taken  on  metal- 

lined  benches? 

63.  Are  conduit  systems  generally  grounded  by  faults? 

64.  Name  twenty  features  of  controller  inspection. 

65.  Are   controller   frames   grounded   on  ground   return 

systems?     Why? 

66.  Are  they  internally  grounded?     Externally?     How? 

67.  How  are  controller  frames  tested  for  ground? 

68.  Is  it  customary  to  ground  metallic  return  controllers? 

69.  Will  an  open  circuit  in  one  controller  affect  operation 

in  both? 

70.  An  open  circuit  affects  both  ends  of  a  car;     is  it  in  a 

controller? 

71.  Applying  power  with  reverses  oppositely  set,  results 

how? 

72.  How  can  the  resistance  of  a  starting  coil  be  measured? 


138  MISCELLANEOUS  TESTS  OF 

73.  What  best  governs  the  resistance  of  a  starting  coil? 

74.  A  coil  starts  a  car  smoothly;    how  would  it  start  a 

lighter  car?    A  heavier  car?     What  is  the  best  test 
for  starting  coils? 

75.  If  a  coil  heats  too  much,  what  should  be  done? 

76.  In  changing  its  current  capacity,  is  resistance  con- 

sidered? 

77.  Do  standard  coils  minimize  controller  abuses? 

78.  Do  standard  coils  affect  circuit-breaker  adjustments? 

How? 

79.  Define  starting  coil  section  test.     Describe  the  test. 

80.  Voltage  applied  to  a  series  circuit  distributes  how? 

81.  In  section  tests,  why  must  sets  of  drops  be  repeated? 

82.  Give  an  empirical  rule  for  sectioning  starting  coils. 

83.  Is  the  section  test  adapted  to  locating  starting  coil 

faults? 

84.  What  is  meant  by  trial  notching  with  a  starting  coil? 

85.  How  will  cars  start  with  resistance  too  low?     Too 

high? 

86.  What  conditions  must  be  considered  in  insulating 

coils? 

87.  Can  a  poorly  insulated  coil  or  hanger  shock  a  pas- 


senger 


88.  Describe  the  voltmeter  test  for  starting  coil  insula- 

tion.    For  leakage  path  resistance.     For  probable 
voltage  of  a  shock. 

89.  What  are  the  spark  points  of  a  lightning  arrester? 

The  air  gap? 

90.  How  does  a  broken  trolley  or  ground  wire  affect 

arrester  operation? 

91.  Should  the  air-gap  of  an  arrester  be  adjusted?  How 

and    to    what   thickness?      State   precautions   in 
applying  the  gage. 

92.  How  can  the  arrester  trolley  and  ground  wires  be 

tested  for  continuity? 

93.  Does  location  of  trolley  tap  affect  manner  of  test? 

94.  Do  all  types  of  arrester  employ  an  air-gap? 


ELECTRIC  CAR  EQUIPMENT  139 

95.  How  will  open  circuit  in  the  lightning  path  affect 

operation? 

96.  How  will  open  circuit  in  the  blow-out   coil  path 

affect  operation? 

97.  What  is  meant  by  the  operating  test  on  arresters? 

98.  Why  should  an  air-gap  be  thinner  than  insulation 

on  devices? 

99.  When  is  it  most    important  that    arresters  be  in- 

spected ? 

100.  How  may  the  effectiveness  of  the  blow-out  device 

be  tested  ? 

101.  What  is  the  object  of  the   extra   resistance  in  the 

test? 

102.  Does  trolley  current  follow  a  lightning  discharge  to 

ground  ? 

103.  What  is  the  object  of  motor  rotation  test?    Give 

connections  ? 

104.  How  are  motions  of  car  and  armature  related? 

105.  What  signs  have  the  A's,  F's  and  E's  in  controllers? 

106.  Do  resistance   connections  affect   direction  of  car 

motion  ? 

107.  How  will  changing  field  jumper  to  other  side  of 

motor  result  ? 

108.  Why  is  it  desirable  to  make  top  field  leads  positive? 

109.  Why  are  armature  wires  crossed  in  No.  2  controller? 

110.  Describe  cable  tagging,  stating  precautions  to  be 

taken. 

111.  How  does  systematic  tagging  save  labor  in  equip- 

ping? 

112.  Is  crossing  of  armature  wires  ever  left  to  the  wire- 

men? 

113.  What  is  the  cable  insulation  test?     How  made  on 

piped  cars? 

114.  Is  high  voltage  test  necessary  on  cars  that  are  not 

piped? 

115.  Define  brush  spacing.     Radial  alinement.     Sym- 

metry of  set. 


140  MISCELLANEOUS  TESTS  OF 

116.  Why  do  brushes  span  fewer  bars  on  an  old  commu- 

tator than  on  a  new  one  of  the  same  kind  ? 

117.  What  is  the  radiality  requirement  of  bevel  edge 

brushes  ? 

118.  On  a  level  surface  car  motor,  where  is  the  line  of 

symmetry  ? 

119.  Why  are  hand  holes  shifted?     State  the  effect  on 

symmetry. 

120.  Name  two  types  of  brush  holders.     Give  character- 

istic of  yoke  type. 

121.  Of  what  type  are  most  General  Electric  railway  motor 

brush  holders?     Westinghouse? 

122.  Can   a   properly   installed   independent   holder   set 

brushes  off? 

123.  To  what  main  irregularity  is  this  type  liable?     The 

yoke  type? 

124.  How  do  variable  shrinkages  affect  the  set  of  holders  ? 

125.  What  precautions  must  be  had  in  regard  to  yoke 

wood?    Is  it  affected  by  heat?    Are  factory  yokes 
specially  treated? 

126.  What  is  meant  by  wrong  brush  spacing? 

127.  What  is  the  symptom  of  displacement  of  one  holder  ? 

Two? 

128.  Which  is  preferable,  brushes  too  close    or  too  far 

apart  ? 

129.  State  the  effect  of  lack  of  symmetry.     How  is  arma- 

ture reaction  involved  ? 

130.  What  is  the  initial  effect  of  lack  of  radial  alinement  ? 

131.  What  is  its  effect  as  the  commutator  wears? 

132.  How  is  the  set  affected  by  a  long  bracket  ?    A  short 

bracket  ? 

133.  How  do  defects  of  radial  alinement  and  yoke  height 

differ? 

134.  Define  canted  brush.     To  what  may  it  be  due? 

135.  How  can  yoke  fault  be  distinguished  from  holder 

fault? 

136.  What  may  cause  canting  of  an  independent  holder? 


ELECTRIC  CAR  EQUIPMENT  141 

137.  How   does  bearing  wear  affect   brush  set?      How 

remedied  ? 

138.  Excessive  brush  pressure  results  how?     How,  defi- 

cient pressure? 

139.  What    operating    conditions    govern    the    pressure 

required  ? 

140.  How  is  brush  pressure  expressed?     In  what  units 

generally  ? 

141.  Between  what  limits  do  brush  pressures  vary? 

142.  How  can  pressure  be  measured?    What  precautions 

are  taken? 

143.  How  are  the  contact  areas  of  straight  and  beveled 

brushes  found  ?    The  pressure  in  pounds  per  square 
inch  is  calculated  how  ? 

144.  Distance   from   commutator  means  what?       What 

should  it  be? 

145.  State  the  effect  if  the  distance  is  too  great.  Too  little. 

146.  How  can  the  distance  be  standardized  with  a  gage? 

147.  What    is    meant    by     (a)  Counting    off    brushes? 

(b)  Center    to    center    count?      (c)  Inside    edge 
count  ?    How  is  center  to  center  count  gotten  ? 

148.  How  may  inside  edge  count  be  gotten  from  center 

to  center  count  ? 

149.  State  the  practical  advantage  of  the  inside  edge 

count. 

150.  What   is  the  immediate   effect   of  error  in   brush 

setting? 

151.  To  what  conditions  may  resulting  sparking  lead? 

152.  How  should  holders  be  made  standard  ?    Maintained 

standard  ? 

153.  How  may   armature  insulation  be  tested   on  the 

floor? 

154.  How  on  a  car?    Why  are  the  brushes  then  drawn? 

155.  Is  there  a  ground  test  for  uninstalled  shelless  field 

coils? 

156.  Describe  insulation  test   for  installed  fields.      For 

brush  holders. 


142  MISCELLANEOUS  TESTS  OF 

157.  Is  badly  charred  condition  of  a  brush  yoke  always 

evident  ? 

158.  What  is  the  operating  symptom  of  an  open  circuit 

field? 

159.  May  such    open  circuit  ever  be    repaired  without 

opening  the  motor? 

160.  Describe  the  bell  circuit  test  for  open  circuit  field. 

161.  Can  a    fault  show  open  circuit  and    ground  too? 

How  can  it  be  proven  by  test  ? 

162.  Will  one  open  circuit  in  an  armature  open  the  motor 

circuit  ? 

163.  What  is  the  operating  symptom  of  an  open  circuit 

armature  ? 

164.  How  can  open  circuit  in  an  armature  be  detected 

(a)  By    resistance    measurement?      (b)  By   volt- 
meter?   (c)  By  a  second  open  circuit? 

165.  Describe  the  drop  test  for  open  circuit  fields. 

166.  What  is  the  operating  symptom  of  short-circuited 

armature  ? 

167.  How  does  it  differ  in  action  from  a  grounded  arma- 

ture? 

168.  Describe  the  compass  tests  for  installed  and  unin- 

stalled  field  coils.     How  can  the  first  test  be  made 
without  current? 

169.  What  is  the  effect  of  a  reversely-wound  field  coil? 

170.  In  what  other  way  can  the  polarity  of  a  coil  be 

reversed  ? 

171.  Why  is  a  coil  in  error  worse  than  a  wrongly  con- 

nected one? 

172.  What  difficulty  may  be  encountered  in  handling  a 

compass  ? 

173.  What  is  meant  by  carbonized  field  coils?    Is  it  very 

common  ? 

174.  How  can  a  well  carbonized  coil  be  tested  in  the 

motor  ? 

175.  Why  must  the   pole-pieces  be  tight?     How  is  it 

sometimes  done  ? 


ELECTRIC  CAR  EQUIPMENT  143 

176.  In  bench  testing  of  field  coils  how  is  compression 

secured  ? 

177.  Describe  the  combination  test.     Where  and  why  is 

one  turn  cut  ? 

178.  What  does  a  high  insulation  deflection  mean?     A 

low  resistance  drop? 

179.  What  advantage  has  the  combined  test  over  the 

resistance  test  ? 

180.  What  does  zero  insulation  deflection  mean?    Maxi- 

mum resistance  drop? 

181.  How  can  the  cut  field  turn  be  easily  repaired  ? 

182.  What  is  meant  by  testing  armature  clearance? 

183.  Describe  the  test  by  light.     By  gage.     By  schedule. 

184.  State  the  disadvantage  of  a  wedge-shaped  gage. 

185.  What  is  the  life  of  a  A  in.  of  well  lubricated  babbitt  ? 

186.  What  does  a  hot  motor  mean  and  what  condition 

does  it  indicate? 

187.  How  is  armature  rubbing  apt  to  affect  breakers  and 

fuses  ? 

188.  Do  armatures  ever  rub  the  upper  pole-pieces? 

189.  Do  pole-pieces  ever  go  down  on  the  armature? 

190.  Can    rubbing    be    caused    by    eccentric    bearings? 

Worn  housings? 

191.  How    are    air-gap    thickness    and    motor   sparking 

related  ? 

192.  What  is  the  object  of  a  motor  balance  test? 

193.  How  is  motor  balance  affected  by  (a)  Open  motor 

frame?  (b)  A  baked,  short-circuited  or  wrongly 
connected  field  coil  ?  (c)  Coil  wound  with  wrong 
size  of  wire?  (d)  .Dissimilar  armatures?  (e) 
Difference  in  gearing  or  wheel  sizes?  (f)  Differ- 
ence in  brush  set  ? 

194.  Assuming  balance,  state  the  voltage  distribution  in 

series. 

195.  Assuming  balance,   state   the   current   division  in 

parallel. 


144  MISCELLANEOUS  TESTS  OF 

196.  Where  a  balance  test  shows  discrepancy,  what  must 

be  done  ? 

197.  Describe  the  voltmeter  balance  test  on  a  two-motor 

car. 

198.  Can  such  a  test  be  made  with  a  single  voltmeter? 

How  ? 

199.  What  difference  in  readings  is  considered   safe  tc 

pass? 

200.  Why  will  the  sum  of  the  readings  be  less  than  line 

voltage  ? 

201.  Should    readings    be    simultaneous?      Approximate 

their  sum. 

202.  How  is  the  per  cent,  difference  in  the  readings  cal- 

culated ? 

203.  Describe   the   voltmeter   balance    test    on    a    four- 

motor  car. 

204.  How  and  why  are  two  of  the  motors  to  be  cut  out  ? 

205.  Are  the  remaining  two  motors  in  series  or  in  parallel  ? 

206.  Describe  the  lamp  balance  test.  State  its  limitations. 

207.  On  what  principles  do  the  lamp  indications  depend  ? 

208.  How  can  the  number  of  lamps  to  be  used  in  series 

be  calculated? 

209.  State  the  reason  for  interchanging  the  test  circuits. 

210.  How  and  why  may  some  of  the  lamps  be  short- 

circuited  ? 

211.  Will    the    test    detect    badly    roasted    or   wrongly 

connected  coils? 

212.  Have  50-volt  lamps  any  advantage  in  such  a  balance 

test? 

213.  How  can  the  voltage  active  per  motor  be  calcu- 

lated? 

214.  Could  the  preceding  tests  be  made  on  motors  in 

parallel? 

215.  Could  the  volts  per  motor  differ  and  the  amperes 

per  motor  not  ? 

216.  Could  the  motors  take  the  same  voltage  but  different 

current  ? 


ELECTRIC  CAR  EQUIPMENT  145 

217.  With    motors    in    series    why    cannot    ammeters 

indicate  usefully? 

218.  With   motors   in    parallel   why    cannot   voltmeters 

indicate  usefully? 

219.  Could  ammeters  in  series  indicate  differently  ?  Why  ? 

220.  Could  voltmeters  in   parallel  indicate  differently: 

Why? 

221.  Why  are  the  ammeters  cut  in  with  the  motor  fields? 

222.  When  must  they  be  cut  in  with  the  motor  arma- 

tures ? 

223.  Describe  the  ammeter  balance  test  on  a  four-motor 

car. 

224.  Why  is  it  unnecessary  to  separate  the  motors  ? 

225.  Can  balance  tests  be  made  with  milli-voltmeters  ? 

226.  Can  low  reading  voltmeters  be  used  to  make  such  a 

test? 

227.  These  meters  with  their  shunts  constitute  what? 

228.  In  what  circuit  is  the  meter  shunt  connected  ? 

229.  What  equipment  part  can  be  used  as  low  reading 

voltmeter  shunt  ?    As  milli-voltmeter  shunt  ? 

230.  Need  the  motor  current   corresponding  to  deflec- 

tions be  known  ? 

231.  What  is  meant  by  the  comparison  of  deflections? 

232.  What  precaution  is  to  be  observed  in  the  test  ? 

233.  Describe  the  milli-voltmeter  balance  test  on  a  two- 

motor  car. 

234.  Why  is  it  undesirable  that  the  shunts  heat?     How 

avoided  ? 

235.  What  precaution  is  taken  in  connecting  the  meters? 

236.  How  can  the  meters  be  calibrated  (a)  To  read  the 

same?     (b)  To  read  direct?     (c)  One  to  read  in 
terms  of  the  other? 

237.  What   is   meant   by    (a)    Calibrating?      (b)    Direct 

reading  ? 

238.  Can  milli-voltmeters  be  bought  with  direct  reading 

shunts? 

239.  Will  the  shunt  of  one  meter  do  for  another  meter? 


146  MISCELLANEOUS  TESTS  OF 

240.  How   can   a  balance  test  be  run  with  one   milli- 

voltmeter  ? 

241.  State  the  objection  to  using  one  meter  in  a  balance 

test. 

242.  Of  what   value   are   balance   tests  in   looking   for 

carbonization  ? 

243.  When  is  its  value  a  minimum  ?     How  can  its  value 

be  improved  ? 

244.  Will  it  show  up  baking  before  it  causes  operating 

troubles? 

245.  What  is  the  first  operating  symptom  of  carboniza- 

tion? 

246.  How  is  it  apt  to  affect  car  fuses  and  circuit-breakers  ? 

247.  What  are  the  objects  of  factory  and  shop  motor  heat 

tests? 

248.  How  do  carbonized  fields  affect  motor  lubricant  ? 

249.  How  are  field  strength  and  motor  current  related  on 

a  car? 

250.  Does  this  same  relation  exist  on  the  heating  test 

rack? 

251.  With  same  current,  will  a  baked  field  heat  like  a  good 

one? 

252.  How  is  the  motor  loaded  in  a  rack  heat  test  ? 

253.  For  how  long  is  the  test  run  in  each  direction  ? 

254.  When  is  a  dynamo  said  to  be  self-excited  ?     Sep- 

arately excited  ? 

255.  In   a   self-excited   test,  why   has  each  machine   a 

reverse  switch? 

256.  May   there   be   difficulty   in   making  the   dynamo 

generate  ? 

257.  How  may  this  be  overcome  ?    Explain  the  action  of 

the  fuse. 

258.  How  is  the  load  on  the  motor  regulated? 

259.  How  is  the  dynamo  field  excited  in  the  separately 

excited  test  ? 

260.  Why  are  there  no  reverse  switches  in  the  dynamo 

fields? 


ELECTRIC  CAR  EQUIPMENT  147 

261.  Is  this  test  well  adapted  to  heat  measurements? 

Why  not  ? 

262.  Describe  the  self-excited  test.     Will  it  show  ground 

faults? 

263.  State  how  a  circuit  is  affected  by  one  ground.    Two 

grounds. 

264.  Briefly  describe  the  running  of  a  shop  heat  test. 

265.  Why  is  speed  taken  initially  and  finally  ?    Why  does 

initial  speed  exceed  final?     How  should  current 
be  in  speed  counts  ? 

266.  How  is  speed  at  standard  voltage  gotten  from  the 

test  speed? 

267.  What  other  conditions  are  watched  during  the  shop 

test? 

268.  Briefly  describe  the  temperature  test  on  a  car  motor. 

269.  Why  must  the  temperature  of  the  atmosphere  be 

noted  ? 

270.  How  is  the  rise  in  resistance  of  the  winding  gotten  ? 

How  is  the  temperature  rise  gotten  from  the  rise 
in  resistance? 

271.  How  is  the  final  resistance  of  the  winding  gotten? 

Why  is  the  calculated  temperature  greater  than 
thermometer  reading? 

272.  How  can  fahrenheit  degrees  be  converted  into  centi- 

grade degrees  ?    How  centigrade  into  fahrenheit  ? 

273.  Define   efficiency   of   a   machine.      Its  input.      Its 

output. 

274.  Can  any  machine  give  out  all  the  work  put  into  it  ? 

275.  Is  this  impossibility  related  in  any  way  to  perpetual 

motion? 

276.  Define   commercial   efficiency   of   a   motor.      Elec- 

trical efficiency  of  a  motor. 

277.  How  are  efficiencies  generally  expressed  ? 

278.  How  can  the  decimal  efficiency  be  converted  into 

per  cent,  efficiency? 

279.  Must  the  input  and  output  be  expressed  in  the  same 

units? 


148  MISCELLANEOUS  TESTS  OF 

280.  Which  is  the  greater,  the  cold  or  hot  efficiency  ? 

281.  What  is  internal  resistance?     How  related  to  elec- 

trical efficiency? 

282.  Which  efficiency  interests  buyers,  hot  or  cold  ? 

283.  Must  the  motor  be  heated  before  an  efficiency  test  ? 

Why? 

284.  What  measurements  are  made  in  taking  commer- 

cial efficiency  tests? 

285.  The  electrical  measurements  are  how  made?     The 

mechanical  ? 

286.  Describe  a  brake  and  state  the  object  of  the  water. 

287.  Why  are  the  weights  guarded?     How  is  the  speed 

measured  ? 

288.  How  is  the  brake  power  expressed  in  watts?    How 

reduced  to  horsepower? 

289.  Why  is  the  constant  1.36  used  in  the  conversion  rule  ? 

290.  What  is  the  direct  object  of  energy  absorption  tests  ? 

291.  When  should  heat,  light  and  compressor  circuits  be 

cut  out  ? 

292.  When  should  test  record  start  and  end  ?    How  about 

delays  ? 

293.  Describe  the  watt-hour  meter  test.     Give  connec- 

tions of  meter. 

294.  State  the  advantage  of  the  watt-hour  meter  method. 

Disadvantage. 

295.  What  is  meant  by  the  constant   of  a  watt-hour 

meter  ? 

296.  How  should  the  instrument  be  protected  from  jolts? 

297.  Describe  the  indicating  wattmeter  test.    What  does 

the  reading  indicate  ? 

298.  How  are  the  watt-hours  absorption  calculated  from 

the  readings? 

299.  How  can  equi-spaced  readings  be  gotten  ? 

300.  How    are    the   meters   connected   in   a   voltmeter- 

ammeter  test  ? 

301.  What   means  may  be  taken  to  get   simultaneous 

readings  ? 


ELECTRIC  CAR  EQUIPMENT  149 

302.  What  temptation   must  a  tester  overcome?     How 

must  the  meters  be  supported  ?    What  precaution 
in  regard  to  capacity  ? 

303.  What  is  the  object  of  the  short-circuiting  switch? 

Will  the  ammeter  indicate  with  it  closed  ?    What 
precaution  is  necessary  ? 

304.  How  are  the  completed  readings  handled  ?    What  do 

individual  products  represent?  To  what  readings 
do  they  correspond? 

305.  When  and  how  may  car-weight  be  gotten  by  two 

weighings  ? 

306.  How    may    pound   weight   be   converted   into   ton 

weight  ?    Ton  weight  into  pound  weight  ? 

307.  How    is    total    horsepower    of   equipment    gotten? 

Full  load  current  ? 

308.  In  what  unit  are  current  values  expressed  ? 

309.  The  actual  duration  of  an  absorption  test  means 

what? 

310.  How  can  duration  in  minutes  be  converted  into 

duration  in  hours? 

311.  How  may  distance  generally  be  gotten  ?    How  from 

rail  count  ? 

312.  How  can  distance  in  feet  be  converted  into  distance 

in  miles? 

313.  What  is  the  maximum  voltage  of  the  test  ?     The 

minimum  voltage? 

314.  When  may  a  reading  be  rejected  ?     How  is  it  then 

treated  ? 

315.  How  is  the  average  voltage  of  the  test  obtained  ? 

316.  What  means  total  ammeter  readings?    Total  current 

readings? 

317.  In  what  subsequent  calculations  is  each  used? 

318.  How  are  the  average  current  of  all  and  of  current 

readings  gotten? 

319.  Why  are  the  sums  of  ammeter  and  current  readings 

the  same? 


150  MISCELLANEOUS  TESTS  OF 

320.  What  is  the  maximum  current  reading  of  an  absorp- 

tion test  ? 

321.  In   case   of  short-circuit  what   current    reading  is 

recorded  ? 

322.  In  case  of  an  unrecorded  maximum  reading,  what 

is  done  ? 

323.  Why  are  the  power  and   current  readings  simul- 

taneously zero? 

324.  What  is  the  maximum  power  reading  of  an  absorp- 

tion test  ? 

325.  Do  maximum  power  and  current  readings  necessar- 

ily coincide? 

326.  What  is  meant  by  total  and  actual  power  readings  ? 

327.  In  what  subsequent  calculations  is  each  used  ? 

328.  What  is  the  average  power  of  all  readings  and  how 

obtained  ? 

329.  How  is  the  average  power  of  current  readings  cal- 

culated ? 

330.  How  is  average  speed  gotten?    Define  total  energy 

absorbed. 

331.  How  is  total  energy  expressed  in  watt-hours?     In 

kilowatt-hours  ? 

332.  How   can  kilowatt -hours  be  converted  into  horse- 

power-hours ? 

333.  How  are  the  average  kilowatts  calculated?     When 

used? 

334.  How  are  kilowatt-hours  per  mile  calculated  ?  Kilo- 

watt-hours per  ton  ? 

335.  How  are  kilowatt-hours  per  ton  per  hour  calculated  ? 

Kilowatt -hours  per  ton  per  mile  ? 

336.  How  can  the  absorption  test  be  made  more  instruc- 

tive? 

337.  What  power  information  do  grade  notes  afford  ? 

338.  State    the    objection    to    the    voltmeter-ammeter 

absorption  test. 

339.  State  the  advantages  of  the  method. 


ELECTRIC  CAR  EQUIPMENT  151 

340.  Has  average  volts  multiplied  by  average  amperes 

any  certain  meaning? 

341.  What  is  the  objection  to  using  it  as  the  average 

power  of  the  test  ? 

342.  Describe  the    rail-count,  pole-count    and    minutes 

per  half  mile  speed  tests. 

343.  Define   acceleration.      How   is   the   term   generally 

accepted  ? 

344.  In  what  units  is  acceleration  generally  expressed  ? 

345.  How  can  miles  per  hour  per  second  be  converted 

into  feet  per  second  per  second  and  vice  versa? 

346.  What  is  meant  by  time  of  acceleration  and  how 

obtained  ? 

347.  How  should  correctness  of  the  time  be  insured? 

348.  What  is  meant  by  distance  of  acceleration  and  how 

obtained  ? 

349.  How    are    maximum    and    average    speeds    during 

acceleration  obtained  ? 

350.  How  can  the  average   speed  be  gotten   from  the 

maximum  speed  ? 

351.  What   is   meant   by   force   of   acceleration?      How 

calculated  ? 

352.  What  is  meant  by  horsepower  of  acceleration  ?    How 

is  it  calculated  ? 

353.  Are  the  calculated  force  and  horsepower  of  accelera- 

tion averages? 

354.  Is  the  acceleration  of  an  electric  car  uniform? 

355.  Define  retardation.     To  what  is  it  generally  due  ? 

356.  Is  the  time  required  to  set  a  brake  easily  obtained  ? 

357.  What  advantage  has  an  air-brake  in  this  respect  ? 

358.  How  is  the  force  of  an  air-brake  applied  ?    A  hand- 

brake? 

359.  How  is  accuracy  secured  in  retardation  tests? 

360.  How  are  retardations  in  miles  per  hour  per  second 

and  feet  per  second  per  second  obtained? 

361.  What   do  distance  and   average  speed  of  retarda- 

tion mean  and  how  obtained? 


152  MISCELLANEOUS  TESTS  OF 

362.  What   does  maximum   speed   of  retardation  mean 

and  how  gotten  from  average  speed  ? 

363.  Does  friction  oppose  acceleration  or  retardation  ? 

364.  Why  can  a  car  be  retarded  from  a  given  speed  to 

rest  in  less  time  and  distance  than  it    can   be 
accelerated  to  that  speed  ? 

365.  How     does     controller     handling     affect     uniform 

acceleration  ? 

366.  What  is  usually  the  object  of  an  acceleration  test? 

367.  How  do  motormen's  efforts  at  rapid  acceleration 

result  ? 

368.  What  are  the  objects  of  retardation  tests? 

369.  What  is  meant  by  train  resistance?    By  coasting? 

370.  What  agencies  stop  a  car  coasting  on  an  up  grade? 

371.  Describe  a  train  resistance  test  on  level  track. 

372.  How  is  total  train   resistance   calculated?     Train 

resistance  per  ton  ? 

373.  What  is  meant  by  rise  per  foot  of  a  grade?     How 

calculated  ? 

374.  What  is  meant  by  per  cent,  of  grade?    How  may  it 

be  calculated? 

375.  How  can  the  retarding  effect  of  a  grade  be  calculated  ? 

376.  What  is  meant  by  the  horsepower  of  traction  ? 

377.  How  can  it  be  calculated?    (Two  methods.) 

378.  How  can  the  horsepower  of  traction  on  grades  be 

calculated? 

379.  What  is  meant  by  the  total  horsepower  of  operation  ? 

380.  How  can  a  body  be  removed  from  a  live  conductor 

in  mid -air? 

381.  What  precaution  must  be  taken  if  the  body  is  on  the 

surface  ? 

382.  In    artificial    respiration,    why    are    the    shoulders 

raised  ? 

383.  What   motions   are   used   to   expand   the   victim's 

chest  ? 

384.  The  position  for  chest  expansion  is  held  how  long? 


ELECTRIC  CAR  EQUIPMENT  153 

385.  How  many  times  per  minute  should  the  complete 

cycle  of  operations  be  repeated  and  for  how  long 
should  they  be  continued  ? 

386.  What  tongue  movements  should  accompany  arti- 

ficial respiration? 

387.  If  the  teeth  are  clenched,  how  may  they  be  parted  ? 

388.  Does  cold  water  dashed  in  the  face  induce  respira- 

tion? 

389.  Does  brisk  rubbing  of  the  spine  induce  a  gasp  ? 

390.  What  effect  has  alternate  warming  and  cooling  of 

the  region  over  the  heart  ? 

391.  Should   stimulants  be   poured  down  the  patient's 

throat  ? 

392.  Give  a  good  application  for  electric  burns. 

393.  In  emergency  cases  how  may  the  mixture  be  applied 

to  body  burns? 


INDEX 


Armature, 

clearance  of,  66-69 
ground  in,  60 
insulation  of,  55 
open  circuit,  57-59 
short  circuit,  60 
wear  of,  47 

Brush  holders, 

alinement  of,  42-45 

wear  of  armature,  47 
Brush  maintenance,  54 

miscellany,  51-56 

pressure,  48-50 

spacing,  45 
Burns,  133 

Canted  brushes 

commutator      "counting 

off,"  47 

height  of,  bracket,  46 
symmetry  of,  43 
types  of,  44 

Car-wiring  cables,  39-40 
Circuit  breakers, 

adjustment  of,  ammeter 

method,  11 
adjustment       of,       limit 

breaker  method,  12 
periodic  tests  of ,  10 
Copper  wire  used  as  fuse,  8 


Dynamos, 

self  excited,  84 
separately  excited,  85 
efficiency  of,  commercial, 

90 
efficiency  of /electrical,  90 

Energy,  absorption  of,  see 
tests 

Field  coils,  see  tests 
Fuses,  see  tests 

Help  to  injured,  131 

Insulation, 

of  armature,  55 
of  brush  holder,  56 
of  car  cable,  40 
of  conduit,  5 
of  field  coil,  55 
of  starting  coil,  29 

Lightning  arresters, 
air  gap  adjustment,  35 
connections  of,  33-34 
operating,  35 

Millivoltmeter  to  Calibrate. 

80-81 
Motor — see  tests 


Pressure 
trolley 


see  tests 
see  tests,  1 


154 


INDEX 


155 


Shock,  aid  in  case  of,  131 
Starting  coil, 

resistance    of — see    tests, 
25 

Temperature,  rise,  calcu- 
lated from  the  increase  in 
resistance,  88 

Test  lines,  method  of  at- 
taching, 13-14 

TESTS 

Acceleration  tests,  114 
Armature  test    for    ground 

in,  60 

for  insulation,  55 
for  open  circuit,  57-59 
for  short  circuit,  60 

Balance  test,  71-78 

Brush     holder,     insulation 

test,  56 
pressure  test,  49 

Car-wiring  cable  insulation 

test,  40 
Controllers, 

Electrical  tests, 
for  ground  in,  21 
for  open  circuit  in,  18 
for  short  circuit  in,  20 
inspection  of,  22 
Mechanical  tests, 

for  alinement,  16-17 
for  interference,  15 
for  interlocks,  15 


Controllers — Continued 
for  notch  spacing,  17 
precautions,  23 

Efficiency  test, 

for  commercial  efficiency, 
92 

for  electrical  efficiency,  91 
Energy  absorption  tests, 

by  integrating  wattmeter 
method,  96 

by  volt -ammeter  method, 
97 

by  watt  hour  meter  meth- 
od, 95 

Field  coils  tests. 

for  carbonization,  63-66- 
82 

for  insulation,  55 

for  open  circuit,  56 

for  polarity,  61-62 

for  short  circuit,  59 
Fuses,  tests  for, 

blowing  test,  7 

calculating  capacity  of 
copper  wire,  8 

instantaneous  test,  7 

operating  test,  8 

requirements  for  test,  9 

time  element,  7* 

Heat  test,  83 

Horsepower      of      traction 

tests,  125 

total  tests,  128 


156 


INDEX 


Lightning    arresters,    tests, 

Retardation  test,  119 

35 

Speed  test,  112 

Motor  balance  test, 

Starting  coils, 

on  two-motor  car,  71,  74, 

insulation  test,  29 

76,  78 

section  test,  25 

on  four-motor  car,  73-78 

shock  test,  30 

heat  test,  83 

Temperature  test,  88 

Pressure  tests, 

Train  resistance  test,  122 

conduit    4 

Time  element  of  fuse,  7 

third  rail,  6 

Trolley  —  see  tests 

trolley,  1-3 

Water  rheostat,  13 

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